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HANDBOOK OF CHEMISTRY, 



FOR 



SCHOOL AND HOME USE. 



BY 



. Wt J. ROLFE, 

FORMERLY HEAD MASTER OF THE HIGH SCHOOL, CAMBRIDGE.. MASS. ; 



^ AND 

J. A. GILLET, 

PROFBSSOR OF MATHEMATICS AND PHYSICS IN THE FEMALE NORMAL AND HIGH 
SCHOOL OF THE CITY OF NEW YORK. 






NEW YORK AND CHICAGO : A 
WOOLWORTH, AINSWORTH, & CO. 



Entered according to Act of Congress, in the year 1874, by 

WOOLWORTH, AINSWORTH, & CO. 
In the Office of the Librarian of Congress at Washington. 



By the same Authors, 

HANDBOOK OF NATURAL PHILOSOPHY. 
HANDBOOK OF THE STARS. 

These are elementary manuals of Natural Philosophy and Astronomy, on the same 
plan as this book. In each of the three, the more difficult and theoretical portions of 
the subject are treated in the Appendix. 

Also, 

THE CAMBRIDGE COURSE OF PHYSICS, 

IN THREE VOLUMES! 

I. CHEMISTRY. 
II. NATURAL PHILOSOPHY. 
III. ASTRONOMY. 



PREFACE 

TO SECOND EDITION. 



We have prepared this book at the urgent re- 
quest of many teachers who desire something 'easier 
and briefer than the " Chemistry " of the Cambridge 
Course of Physics. This is a more elementary 
work, and therefore less theoretical. It is, in a 
word, a manual of the elementary facts and princi- 
ples of Chemistry. While there is little that is 
strictly theoretical in the body of the book, we have 
not forgotten that Chemistry is not a mere mass of 
dead facts, but a living science. We have there- 
fore aimed to present the facts in such a way as to 
awaken a love for the science itself, no less than to 
show its utility. Our object has been not only 
to describe the properties of the leading elements 
and compounds, but also to show the wonderful part 
played by the chemical force in nature, as well 
as to illustrate its practical applications in the arts. 
We have endeavored to give the young student a 
glimpse of — 

"the circle of eternal change, 

Which is the me ui nature," — 

a life whose fountain-head is the sun, and whose 



IV PREFACE. 

processes we trace in the chemistry of the atmos- 
phere. In this indirect but natural way, we have 
introduced as much of organic chemistry as could 
well find place in an elementary manual. 

The metals we have grouped more according to 
their uses than according to their chemical relations, 
with a view to make the subject less dry and more 
practical. 

It is difficult to write a book suited to the wants 
of different schools, or even of successive classes in 
the same school ; since the schools vary in grade, 
and the classes in ability. We have attempted to 
meet this difficulty by putting into the body of the 
book the simpler and more practical portions of the • 
subject, which can be readily mastered by young 
pupils of average ability, and by adding in the 
Appendix an outline of some of the more important 
principles of chemical philosophy. la this way, 
the simpler and the more difficult parts, instead of 
being confusedly mixed together, distinguished 
merely by the common and clumsy expedient of 
coarse and fine print, are treated separately, so 
that each may be complete in itself. At the 
same time, the two parts do not overlap, but 
form successive chapters progressively arranged. 
Our experience as teachers has convinced us, that 
this is, on the whole, the best method of meeting 
the wants of successive classes ; and the marked 
favor with* which our ?r Handbook of the Stars," 
an elementary " Astronomy " on precisely the same 



PREFACE. V 

plan, has been received, shows that the experience 
of many of our fellow-teachers has been pretty much 
the same as our own. 

We have not forgotten that the theories of chem- 
istry have been revolutionized within a few years ; 
and we have of course used the new symbols and 
notation, without which it is as impossible to teach 
modern chemistry as it would be to teach modern 
astronomy in the language of the old astrologers. 
Until within a year or two, there was some excuse 
for clinging to the old notation, as rival systems 
were contending for the supremacy. But even as 
long ago as October, 1866, Miller, the first English 
authority on the subject, wrote as follows : " The 
change in notation is certain to be adopted, since 
in none of the recent investigations in this country, 
and in very few of those on the Continent, is the old 
method made use of." Since that time, the system 
of symbols and notation used bv us in this book has 
been formally adopted by the Chemical Society 
of London, whose decision is recognized as law in 
England ; and it is now taught in Harvard College, 
which will certainly be acknowledged as one of the 
highest authorities in this country. 

In the chapter on the Chemistry of the Atmos- 
phere, we have been especially indebted to the Lec- 
tures on "Religion and Chemistry" (New York, 
1866), by Professor Josiah P. Cooke, Jr., of Harvard 
College ; and in the chapters on Quantivalence and 
Molecular Structure, in the Appendix, we have 



VI PREFACE. 



drawn freely from the " First Principles of Chemi- 
cal Philosophy" (Cambridge, 1868), by the same 
eminent author. His remarkable power of present- 
ing difficult subjects in a way at once clear and 
attractive, makes these books especially valuable to 
the teacher. 

We have been under obligations, also, to Miller's 
"Elements of Chemistry" (London, 1866), and 
Roscoe's "Elementary Chemistry" {New Edition, 
London and New York, 1869). These books, as 
well as Hofmann's "Modern Chemistry " (London, 
1865), and Wurtz's "Introduction to Chemical Phil- 
osophy" (London, 1867), the teacher will find use- 
ful for purposes of reference. 

Cambridge, January 1, 1S70. 



^^ Teachers will observe that, except in the Appendix, 
either the old chemical name or the ordinary commercial name 
of the substance is generally added, in parentheses, to the new 
chemical name. 



TABLE OF CONTENTS. 



Page 

THE NON-METALLIC ELEMENTS 3. 

Compounds and Elements 3' 

Oxygen ... 10 

Hydrogen 15 

Water 17 

Nitrogen . * . . ...... 21 

Carbon ................. 28 

Sulphur .......... 30 

Chlorine 36 

Bromine 40 

Iodine . . ........ 40 

Fluorine 41 

Phosphorus ................ 42 

Arsenic ................. 43 

Boron .......... 44 

Silicon 44 

Summary . 45 

THE METALS .49 

General Properties of the Metals ...... 49 

The Most Useful Metals 51 

The Noble Metals 64 

Less Useful Metals 71 

Metals not used in a Free State, but valuable 

for their Salts 83 

The Rarer Metals 89 

Summary 90 

CHEMISTRY OF THE ATMOSPHERE 91 

Combustion. 9L 



Vlll CONTENTS. 

Page 

Slow Combustion 100 

The Growth of Plants ..-...,.. 108 

Natural Vegetable Products . . . . . . . . 120 

Summary . . 131 

DESTRUCTIVE DISTILLATION AND ITS PROD- 
UCTS 133 

Coal-Oils 139 

Coal-Gas ....... . 142 

Illumination 145 

Summary 149 

FERMENTATION 151 

Summary 159 

APPENDIX 161 

QUANTIVALENCE l6l 

Molecular Structure 164 

The Spectroscope and its Applications in Chem- 
istry 168 

Dissociation 171 

Photography 175 

The Chemistry of Luminous Flames 178 

Exercises and Problems 181 

Notes on Experiments 185 

Questions for Review and Examination . . . 197 

INDEX '. 205 



HANDBOOK OF CHEMISTRY. 



THE NON-METALLIC ELEMENTS. 



COMPOUNDS AND ELEMENTS. 

i . Muriatic Acid. — Into a bottle arranged as shown 
in Figure I, put a few bits of zinc, and pour a little muri- 
atic acid over them. Effervescence at once takes place, 
and a colorless gas passes through the bent tube into the 
jar, which has been previously filled with water, and in- 




SW 



verted over the trough. When the jar is full of gas, raise 
it from the water, and apply a lighted taper to its mouth. 
The gas takes fire with a slight explosion, and burns with a 
pale flame. This gas is called hydrogen, and comes from 
the muriatic acid. 

Pour a little of the muriatic acid into a flask (Figure 2), 
add a little black oxide of manganese, mix them thor- 



COMPOUNDS AND ELEMENTS. 



oughly, and heat gently. A greenish-yellow gas passes 
into the jar inverted over the water-trough. When the 
jar is full, close its mouth with a glass plate, remove it 
from the trough, and set it on the table. Moisten a piece 
of litmus-paper or colored cotton cloth, and hold it inside 
the jar. It will be instantly bleached. This gas is called 
chlorine, and, like the hydrogen, comes from the muri- 

Fig. 2. 




atic acid. Chlorine may be recognized by its bleaching 
power, and also by its color and its suffocating odor. 

We have now got from muriatic acid two gases, hydro- 
gen and chlorine. 

If a small glass jar be filled with equal parts of these 
two gases, and a light be applied to its mouth, the mix- 
ture will take fire with an explosion. If a little dish of 
ammonia be standing by, a dense white cloud will appear 
when the gases burn. 

Now this cloud shows that muriatic acid has been 
produced ; for, if we dip a glass rod in muriatic acid, 
and hold it over the ammonia, the white cloud at 
once appears. 

Muriatic acid, then, contains nothing but hydrogen and 
chlorine. 



COMPOUNDS AND ELEMENTS. 



2. Water. — If a bit of sodium be thrust beneath the 
mouth of an inverted jar, filled with water, as shown in 
Figure 3, bubbles of gas rise and fill the jar. On raising 
the jar, and applying a taper to its mouth, we see, by the 
way in which the gas takes fire, that it is hydrogen. 

Fill a tall glass jar with chlorine water (that is, water 
which has absorbed chlorine gas), invert it, with its 

Fig. 3. 




mouth in a shallow dish of water, and leave it for ten or 
twelve hours in the sunshine. Bubbles of gas will be 
seen to rise, and collect in the top of the jar. If now we 
set the jar upright, and plunge a lighted taper into the 
gas, the taper burns much more brightly than in the air. 
This gas is called oxygen. 

We have thus got hydrogen and oxygen from water. 
If, now, we burn a jet of hydrogen in a jar of oxygen, 
moisture will collect on the sides. This moisture is 
water, and comes from the union of the hydrogen and 
the oxygen. This shows that there is nothing but oxygen 
and hydrogen in water. 



6 



COMPOUNDS AND ELEMENTS. 



Fig. 4. 



3. Ammonia. — Fill With chlorine a long glass tube, 

closed at one end. Close 
the other end with a cork, 
through which passes a drop- 
ping tube. (Figure 4.) If, 
now, a little ammonia be 
dropped into the tube, flashes 
of light and dense white 
fumes appear within; Next 
allow water to run into the 
tube as long as it will, and 
test the gas which remains, 
by putting a piece of litmus- 
paper into it. The paper is 
not bleached, hence the gas 
is not chlorine. Plunge a 
lighted taper into it, and it 
goes out, and the gas does 
not take fire ; hence the gas 
is neither oxygen nor hydro- 
gen. It is niti'ogeit, and it 
always, as in this case, ex- 

tinguishes a lighted taper. 

This nitrogen must have come from the ammonia, since 
there was no nitrogen in the water poured into the tube. 

The white fumes which appeared in the tube, when 
the ammonia was dropped in, showed that muriatic acid 
was formed. Now we have learned that muriatic acid is 
made up of chlorine and hydrogen. The hydrogen must 
also have come from the ammonia. 

Ammonia, then, contains nitrogen and hydrogen. It 
has been found by experiment that it contains nothing but 
these two gases. 

4. Co?npounds and Elements. — We have now seen 
that muriatic acid, water, and ammonia, are made up of 




COMPOUNDS AND ELEMENTS. 



other substances, which we can separate from them. In 
other words, they are compound substances, and we have 
decomposed them. But no means has been found of de- 
composing oxygen, hydrogen, chlorine, and nitrogen into 
simpler substances. These, and other substances which 
cannot be decomposed, are called elements. 

Most substances with which we are familiar are com- 
pounds. The metals, however, are all elements. 

There are only about sixty-five elements in all, and 
many of these are very rare substances. 

5. Names and Symbols of Elements. — Elements have 
been divided into two classes, metallic and non-metallic. 
The following list contains the names of the most 
important elements usually put in each class, together 
with the abbreviations of these names commonly used. 
These abbreviations are called symbols. 



NON-METALLIC ELEMENTS. 



Name. 


SYMBOL 


Boron 


B 


Bromine 


Br 


Carbon 


C 


Chlorine 


CI 


Fluorine 


F 


Hydrogen 


H 



Atomic 
Weight. 


Name. 


Symbol 


Atomic 
Weight. 


11 


Iodine 


I 


127 


80 


Nitrogen 


N 


14 


12 


Oxygen 





16 


35-5 


Phosphorus 


P 


3i 


19 


Silicou 


Si 


28 


1 


Sulphur 


s 


32 



METALLIC ELEMENTS. 



Aluminium 


Al 


27.4 


Magnesium 


Mg 


24 


Antimony {stibium) 


Sb 


122 


Manganese 


Mn 


55 


Arsenic 


As 


75 


Mercury {hydrargyrum) Hg 


200 


Barium 


Ba 


137 


Nickel 


Ni 


58-7 


Bismuth 


Bi 


210 


Platinum 


Pt 


197-5 


Calcium 


Ca 


40 


Potassium {kalium) 


K 


39 


Chromium 


Cr 


S2.5 


Silver {argentum) 


Ag 


108 


Cobalt 


Co 


58.7 


Sodium {natrium) 


Na 


23 


Copper {cuprum) 


Cu 


6 3 -5 


Strontium 


Sr 


8 7 -5 


Gold {ai<rum) 


Au 


197 


Tin {stannum) 


Sn 


118 


Iron {ferrum) 


Fe 


56 


Zinc 


Zn 


65.2 


Lead {plumbum) 


Pb 


207 


' 







s 



COMPOUNDS AND ELEMENTS. 



It will be noticed that in some cases the symbol is an 
abbreviation of the Latin name of the element. 

6. Affinity. — The force which draws elements toge- 
ther, and locks them up in compounds, is called affi?tity, 
or chemical force. 

One of the characteristics of this force is, that it cJianges 
the properties of the substances which it brings together. 
It not only unites different substances, but unites them so 
as to form a new substance. It combines them. 

This characteristic is well illustrated in the case of 
water, a substance wholly unlike hydrogen, which is 
combustible, and oxygen, which aids combustion. 

The second characteristic of affinity is, that it always 
acts between definite quantities of matter. This may 
be illustrated by the following experiment : — 

Partially fill the closed arm of the U tube (Figure 5) 
with a mixture of hydrogen and oxy- 
gen, using more than twice as much 
hydrogen as oxygen. Explode the mix- 
ture by means of an electric spark from 
a Leyden jar. The hydrogen and the 
oxygen combine to form water, but 
some gas remains, which, if tested with 
a taper, is found to be hydrogen. 

If now we put into the tube a mix- 
ture containing less than twice as much 
Hf hydrogen as oxygen, the gas which re- 
W mains after the explosion is found to be 
oxygen. 
In both cases, the oxygen combines with exactly twice 
its bulk of hydrogen, and this will be true in whatever 
proportions the gases may be mixed. 

This experiment also illustrates the third characteristic 
of affinity, which is, that it is often dormant until it is 
roused to activity by heat, or some other force. The 




COMPOUNDS AND ELEMENTS. 9 

oxygen and the hydrogen showed no disposition to com- 
bine until the spark was sent through them. 

7. Molecules and Atoms. — It is supposed that all 
bodies are made up of small particles called molecules, 
and that these molecules are made up of smaller parti- 
cles, which are called ato??2s (that is, not to be divided}, 
since we are not able to subdivide them. 

In an elementary substance, the atoms are supposed to 
be all alike in form and weight, but those of one element 
differ in weight from those of another. In a compound sub- 
stance, the molecules are supposed to be alike, each being 
made up of a fixed number of atoms of each of the com- 
ponent elements ; but the molecules of one compound 
differ from those of another in their atomic constitution. 
This theory of the composition of substances is called the 
atomic theory. 

Thus the molecules of muriatic acid are supposed to 
be made up of one atom of hydrogen and o?ie of chlorine ; 
the molecules of water to be made up of two atoms of 
hydrogen and one of oxygen ; and the molecules of am- 
monia to be made up of three atoms of hydrogen and one 
of nitrogen. 

8. Symbols of Compounds. — The symbol of a com- 
pound is made up of the symbols of its elements. It also 
indicates the atomic constitution of the molecules of the 
compound. The symbol of each element represents one 
atom of that element. If there is more than one atom of 
the element in the molecule, this is indicated by a small 
figure placed at the right of the symbol. Thus the sym- 
bol for muriatic acid is HC1 ; indicating that muriatic 
acid is a compound of hydrogen and chlorine, and that a 
molecule of muriatic* acid is made up of one atom of 
hydrogen and one of chlorine. The symbol for water is 
H 2 0, since water is a compound, whose molecule con- 
tains two atoms of hydrogen and one of oxygen. The 



IO 



COMPOUNDS AND ELEMENTS. 



symbol of ammonia is H 3 N, its molecule being made up 
of three atoms of hydrogen and one of nitrogen. 

9. Atomic Weights. — According to the atomic theory, 
an atom of chlorine weighs 35.5 times as much as an atom 
of hydrogen ; an atom of oxygen weighs 16 times as much 
as one of hydrogen ; and an atom of nitrogen 14 times as 
much as one of hydrogen. If then we represent the 
weight of an atom of hydrogen by 1, the weight of an 
atom of chlorine will be 35.5 ; that of an atom of oxygen, 
16 ; and that of an atom of nitrogen, 14. These numbers 
are called the atomic weights of these elements. (5.) 

We now see that the symbol of a compound represents 
not merely the atomic constitution of the compound, but 
also the relative weights of its elements. Thus muriatic 
acid, HC1, contains 1 part by weight of hydrogen to 35.5 
parts by weight of chlorine ; water, H 2 0, contains 2 parts 
by weight of hydrogen to 16 of oxygen ; and ammonia, 
H 3 N, contains 3 parts by weight of hydrogen to 14 of 
nitrogen. 

OXYGEN. 

10. Preparation of Oxygeit. — Oxygen is most readily 
obtained from potassic chlorate (chlorate of potash), a sub- 
stance of whose weight it forms about 40 per cent. The 
chlorate is heated in a flask (Figure 6), and the gas is 

Fig. 6. 




■W/j/lBM^^ 



COMPOUNDS AND ELEMENTS. II 

collected over water. Potassic chlorate is a compound of 
chlorine, potassium, and oxygen, and its symbol is KC10 3 . 
The oxygen is set free by the heat, leaving the chlorine 
and potassium as a compound called potassic chloride. 

A chemical change of this kind is called a reaction, 
and may be expressed in the form of an equation. In 
this case the equation will be — 

KC10 8 = KCl + O a 

indicating that the potassic chlorate, KC10 3 , has been 
broken up into potassic chloride, KC1, and oxygen, O. 

If a small quantity of black oxide of manganese be 
mixed with the potassic chlorate, the gas is given off at a 
much lower temperature, and more gradually. The man- 
ganese, however, undergoes no change in the process. 

ii. Properties of Oxygen. — We have already seen 
(2) that a taper burns much more vividly in oxygen than 
in the air. 

If a piece of charcoal be lighted and plunged into a jar 
of oxygen, it burns with a very brilliant white light. 
Pour now some clear lime-water into the jar, and shake it. 
The liquid becomes milky white, showing that the gas 
has undergone a change ; for oxygen has no effect upon 
lime-water. Charcoal is a form of the element carbon, 
and the oxygen has combined with it. The compound 
produced is called carbonic anhydride {carbonic acid), 
and its composition is represented by the symbol, C0 2 . 

If a bit of sulphur be ignited and put into a jar of oxy- 
gen, it burns with a vivid blue light and a suffocating 
odor. The sulphur and the oxygen have combined to 
form sulphurous anhydride {sulphurous acid), the sym- 
bol of which is S0 2 ., 

Phosphorus burns in oxygen with dazzling brilliancy, 
producing dense, white fumes of phosphoric anhydride 
{phosphoric acid), P 2 5 . 



12 COMPOUNDS AND ELEMENTS. 

Thus far, we have found that substances which burn in 
the air burn more rapidly and more brightly in oxygen. 
If, now, we fasten a bit of wood to a steel watch-spring, 
ignite the wood, and plunge the whole into a jar of oxy- 
gen, the watch-spring takes fire, and burns as readily as a 
splint of wood burns in the air. In this case the iron and 
the oxygen combine, forming a mixture of two oxides of 
iron, FeO, ferrous oxide, and Fe 2 O s , ferric oxide. 

The above experiments illustrate several properties of 
oxygen: (i) the passive state in which it exists tinder 
ordinary circumstances, it being necessary to heat it in 
order to make it combine rapidly with any substance ; (2) 
the intense energy with which it enters into combination 
when once aroused; and (3) the wide range of its affini- 
ties. It combines with every known element, except 
fluorine. 

12. Ozone. — If a series of electric sparks be sent 
through dry oxygen, the gas undergoes a changp. It ac- 
quires more active properties and a peculiar odor from 
which it takes its name, ozone* The odor perceived 
when an electrical machine is worked is owing to the 
presence of ozone. 

If a paper moistened with a solution of potassic iodide 
{iodide of potassium), KI, and starch paste be held op- 
posite a point on the conductor of an electrical machine, 
the paper becomes blue. The iodine is set free by the 
ozone, and unites with the starch, forming a blue com- 
pound, which colors the paper. Ordinary oxygen has no 
such power to separate iodine from its combination with 
potassium. 

There has been much discussion concerning the nature 
of ozone. It appears, however, to be simply oxygen in 
a modified and condensed form. 

* Ozone is derived from a Greek word which means to emit a 
bad odor. 



COMPOUNDS AND ELEMENTS. 1 3 

This partially active state of oxygen is intermediate 
between the active and passive states already mentioned. 

13. Allotropic States. — There are other elements 
which exist in states in which their properties are as un- 
like as those of oxygen and ozone. These different states 
of an element are called allotropic states. 

14. Oxides. — " The simple compounds of the elements 
with oxygen are called oxides, and the specific names of 
the different oxides are formed by placing before the word 
oxide the name of the element, but changing the ter- 
mination into ic or ous, to indicate different degrees of 
oxidation, and using the Latin name of the element in 
preference to the English, both for the sake of euphony 
and in order to secure more general agreement among 
different languages. When the same element unites with 
oxygen in more than two proportions, the Latin preposi- 
tions or numeral adverbs, sub, per, bis, etc., are prefixed 
to the word oxide in order to indicate the additional de- 
grees. Formerly these compounds were called the oxides 
of the different elements, the degrees of oxidation being 
indicated solely by the prefixes." * 

The ending oils indicates a lower degree of oxidation 
than the ending ic. 

15. Acids. — Very many of the non-metallic oxides 
combine with water, forming compounds which turn blue 
litmus-paper red. Such oxides are called acid oxides, or 
anhydrides, and their compounds with water are called 
acids. Thus S0 2 -f- H 2 = H 2 S0 3 . SO a is sulphurous 
a?zhydride, often improperly called sulphurous acid, a 
name which properly belongs to H 2 S0 3 . So H 2 -)- SO s 
(sulphuric anhydride) =H 2 S0 4 (sulphuric acid). 

Here, too, as in the case of oxides, the ending ous 
denotes a lower degree of oxidation than the ending ic. 

* First Principles of Chemical Philosophy. By Josiah P. 
Cooke, Jr., 1868, p. 69. 



14 COMPOUNDS AND ELEMENTS. 

When more than two acids are formed by the same 
elements, the prefixes hypo (=less) and hyper or per 
(more) are used. Thus, hydrogen, chlorine, and oxygen 
form four acids : HCIO, hypochlorous acid; HC10 2 , chlo- 
rous acid; HC10 3 , chloric acid; and HC10 4 , hyper- 
chloric acid, or perchloric acid. 

Acids are often named from all their elements, thus : — 

H.-jSOg, hydric sulphite ; HC10 2 , hydric chlorite; 

H. 2 SG 4 , hydric sulphate; HC10 3 , hydric chlorate; 
HCIO , hydric hypochlorite ; HC10 4 , hydric perchlorate. 

The endings ite and ate in these names indicate oxy- 
gen, and ite the less amount of this element. 

16. Bases. — Many of the metallic oxides combine 
With water to form compounds whose properties are the 
opposite of those of the acids. These are called basic 
oxides, and their compounds with water are called bases. 

Bases are named like acids, as shown above. Thus, — 

•J(K 2 0, potassic oxide, -\- H 2 ) =K.HO, potassic hydrate; 
BaO, baric oxide, -\- H 2 = BaH 2 2 , baric hydrate ; 
FeO, ferrous oxide, -f- H 2 =z FeH 2 2 , ferrous hydrate ; 
Fe 2 3 , ferric oxide, -f-3 H 2 0=Fe 2 H 6 6 , ferric hydrate. 

The potassic and sodic hydrates (KHO and NaHO) 
and some others are called alkalies. 

17. Neutrals. — Oxides which, like water, are neither 
acid nor basic, are called neutral oxides, or neutrals. 

18. Salts. — A metal may take the place of the hydro- 
gen in an acid, and the compound thus formed is called a 
salt. Thus, the metal potassium may .take the place of 
the hydrogen in H 2 S0 3 and H 2 S0 4 , forming the salts 
K 2 S0 3 and K 2 S0 4 . 

Salts are named in the same way as the acids and bases 
already explained. Thus we have — 



K 2 S0 3 , potassic sulphite; 
K 2 S0 4 , potassic sulphate; 
KNOg, potassic nitrate; 



FeSO 4 , ferrous sulphate; 
Fe 2 3 S0 4 , ferric sulphate ; 
KC10 3 , potassic chlorate. 



COMPOUNDS AND ELEMENTS. 



15 



19. Binary and Ternary Compoimds. — Compounds 
like HC1 (muriatic acid), FeO (ferrous oxide), KI (po- 
tassic iodide), etc., which contain two elements, are 
called binary compounds ; and compounds like H 2 S0 4 
(sulphuric acid), KHO (potassic hydrate), FeSG 4 (fer- 
rous sulphate), etc., which contain three elements, are 
called ternary compounds. (See Appendix, VII.) 

HYDROGEN. 

20. Preparation of Hydrogen. — The most conven- 
ient way of preparing hydrogen is by the action of zinc 
on dilute sulphuric acid. The apparatus required is 
shown in Figure 7. 

Fig. 7. 




The reaction between the zinc and the sulphuric acid 
is shown in the following equation : — 

H 2 S0 4 + Zn = Zn S0 4 + H 2 . 

The zinc changes places with the hydrogen, forming the 
salt known as zincic sulphate, or white vitriol, w^hile 
the hydrogen is set free. 

21. Properties of Hydrogen. — If soap-bubbles are 
blown with a mixture of two measures of hydrogen to 
one of oxygen, they will explode violently when touched 
with a lighted taper ; showing the intense energy with 



1 6 COMPOUNDS AND ELEMENTS. 

which hydrogen and oxygen combine at a high temper- 
ature. If a mixture of hydrogen and atmospheric air 
be used, a similar explosion will take place. Hence, in 
preparing hydrogen for experiments, great care must be 
taken to expel all air from the apparatus before any of 
the gas is collected. 

If a small rubber balloon be filled with hydrogen, it 
rises readily in the air, showing that the gas is lighter 
than air. It is, in fact, the lightest substance known, 
being 14.5 times lighter than air, and 16 times lighter 
than oxygen. It was formerly used in filling balloons ; 
but coai-gas, which, though not so light, is much cheap- 
er, is now commonly employed instead. 

The lightness of hydrogen and the energy with which 
it combines "with oxygen, are its two most important 
characteristics. 

22. The Oxy-hydrogen Blowpipe. — The energy with 
which hydrogen and oxygen combine develops intense 
heat. This may be shown by means of the oxy-hydrogen 
blowpipe, represented in Figure 8. The hydrogen is 
Fig. 8. forced through the tube 

H, and the oxygen 
through the tube O; 
and it will be seen that 
H ° ^ the two can mix only at 

the mouth of the jet 
where they are burned, 
so that there is no dan- 
ger of an explosion. The gases may be kept in a gas- 
ometer (Figure 9), or, more conveniently, in gas-bags 
of india-rubber. 

Hold a copper or iron wire in the flame of this blow- 
pipe, and it burns as readily as a pine shaving held in 
the flame of a lamp. A steel watch-spring burns with 
brilliant scintillations. If a bit of zinc be placed on a 




COMPOUNDS AND ELEMENTS. 



17 



Fig. 9. 



piece of charcoal hollowed out for the purpose, and the 
flame of the blowpipe be directed upon it, the metal 
quickly melts and burns. An- 
timony, bismuth, and many 
other metals will burn in the 
same way, each with a char- 
acteristic light. Cast - iron 
burns with a shower of bright 
sparks. Platinum, which is 
one of the most infusible of 
substances, is readily melted, 
and even converted into vapor. 
A small cylinder of lime 
placed in the blowpipe flame 
becomes white-hot, and glows 
with most intense brilliancy, 
forming what is known as 
the lime light or Drununond 
light. When the rays of this 
light have been gathered and 
reflected by a mirror, it has 
been seen at a distance of one hundred miles in full 
daylight. 

WATER. 




23. The Properties of Water. — The most important 
compound of hydrogen is water, which, as we have 
already learned" (2), contains hydrogen and oxygen. 

At ordinary temperatures, water is a clear," colorless 
transparent liquid, without taste or smell. It freezes at 
3 2 , and under the ordinary pressure of the atmosphere 
it boils at about 2 12°. 

It is the most universal solvent known. There are but 
few substances which are not dissolved by it. Even those 
which we call insoluble, generally differ from the rest 



15 COMPOUNDS AND ELEMENTS. 

only in degree. Spring water dissolves lime-rocks, and 
almost all other mineral substances. The beautiful crys- 
tals found in the rocks are almost invariably deposited 
from a solution of the mineral in water, though in many 
cases it may have taken thousands of years to form them. 

Water dissolves almost all gases as well as solids. It 
is on the gases dissolved in the water that all aquatic 
plants and animals live. 

24. Various kinds of Natural Waters. — Owing to 
its solvent powers, water is never found in nature in a state 
of purity. Rain water, collected after long-continued 
wet weather, comes nearest to it ; but even this always 
contains small quantities of atmospheric air, and the gases 
floating in the air. 

Spring- water always contains more or less of saline 
matter, which it has dissolved from the soil. The salts 
most frequently found in it are common salt, calcic car- 
bonate and sulphate (carbonate and sulphate of lime), 
and magnesic carbonate and sulphate (carbonate and 
sulphate of magnesia). Most spring water contains car- 
bonic acid, to which it owes its sprightly taste. 

Mineral waters are waters which contain an unusually 
large proportion of any of the salts just named, or of other 
and rarer substances. In many cases they have medicinal 
qualities, which vary with the salts held in solution. 
They sometimes contain salts of iron, and are then called 
chalybeate springs. In other instances, carbonic acid is 
so abundant as to give them an effervescent character. 
Less frequently sulphur is the chief ingredient, giving the 
water a nauseous taste and smell. 

Water is familiarly called hard or soft, according to its 
action on soap. Hard waters contain salts of calcium or 
magnesium, which cause the soap to curdle, that is, to 
become insoluble. Soft waters do not contain these salts, 
and dissolve the soap without difficulty. Many hard 



COMPOUNDS AND ELEMENTS. 1 9 

waters become soft by boiling, the salts held in solution 
being deposited, as a fur or crust, on the inside of the 
boiler. 

Sea water contains a large amount of common salt and 
of magnesic chloride (chloride of magnesium), to which 
it owes its saline, bitter taste. Smaller quantities of many 
other salts are found in it. All this matter has been 
washed out of the soil by the rivers which flow into the 
sea. It remains in the sea, since the water which evap- 
orates from the surface is almost perfectly pure ; but the 
surplus is continually taken up by marine plants and ani- 
mals, so that the sea becomes no Salter. 

25. Water in Plants and Animals. — Water consti- 
tutes the greater part of all plants and animals. The 
human body is four-fifths water. In many of the lower 
animals the proportion is much greater. From a sun-fish 
weighing 30 pounds, only 240 grains of solid matter were 
obtained ; so that water makes up about .999 of the 
weight of such animals. The vegetable substances which 
we use for food contain almost as large a percentage 
of water. In potatoes, the fraction is .J^ ; in apples, 
.80 ; in turnips, .90 ; in watermelons, .94 ; and in cucum- 
bers, .97. 

26. Water of Crystallization. — Many salts, in crys- 
tallizing from their solutions, unite with a definite quantity 
of water, which is then called water of crystallization. 
If the salt be heated, the water is driven off, and the crys- 
tals fall to pieces ; but the chemical properties of the sub- 
stance are not altered. Many salts part with this water 
by mere exposure to the air, and effloresce; that is, 
crumble into white powder. Sodic carbonate (carbonate 
of soda) is an efflorescent salt. Other salts, on the con- 
trary, like potassic carbonate (carbonate of potash), ab- 
sorb water from the air, and become moist, or even dis- 
solve ; in which case they are said to deliquesce. 



20 COMPOUNDS AND ELEMENTS. 

27. Uses of Water. — •' On the uses of water it is almost 
needless to enlarge, for they are universally felt and ap- 
preciated. In each of its three physical conditions, the 
blessings which it confers on man are inestimable. As 
ice, it furnishes in northern lands, for months together, a 
solid bridge of communication between distant places : in 
the liquid condition, it is absolutely necessary to the ex- 
istence of vegetable and animal life ; in this shape, too, 
it furnishes to man a continual source of power in the 
flow of streams and rivers ; it supplies one of the most 
convenient channels of communication between places 
widely separated ; and further, it is the storehouse of 
countless myriads of creatures fitted for use as food : in 
the state of vapor, as applied in the steam-engine, it has 
furnished a power which has, in late years, done more 
than any other physical agent to advance civilization, to 
economize time, and to ameliorate the social condition of 
men. In each and all of these points, if rightly consid- 
ered, we must perceive the entire adaptation of this com- 
pound to the ends which it was designed by the Creator 
to fill. 

" Glancing at the physical condition of our planet, we 
cannot fail to be impressed with the important effects pro- 
duced by the movements of water at periods anterior to 
the existence of man, as well as in more recent times. 
To such causes must we refer the formation of sedimen- 
tary rocks, and their arrangement in successive strata 
upon the surface of the earth : even now, observation 
shows that denudation is proceeding at some points, ele- 
vation and filling-up at others ; whilst the accumulation 
of drift, and a variety of other extensive geological 
changes, must be traced to the same ever-acting and 
widely-operating agency. 

" It may further be observed, that there is no form of 
matter which contributes so largely as water to the beauty 



COMPOUNDS AND ELEMENTS. 21 

and variety of the globe which we inhabit. In its solid 
state, we are familiar with it, in the form of blocks of ice, 
of sleet and hail, of hoar-frost fringing every shrub and 
blade of grass, or of snow protecting the tender plant, as 
with a fleecy mantle, from the piercing frosts of winter. 
The rare but splendid spectacles of mock suns, or par- 
helia, are due to the refractive power of floating spicule 
of ice upon the sun's rays. In its liquid condition, as rail 
or dew, it bathes the soil ; and the personal experience 
of all will testify to the charm which the waterfall, 
the rivulet, the stream, or the lake, adds to the beauty 
of the landscape ; whilst few can behold unmoved 
the unbounded expanse of ocean, which, whether mo- 
tionless, or heaving with the gently undulating tide, or 
when lashed into fury by the storm which sweeps over its 
surface, seems to remind man of his own insignificance, 
and of the power of Him who alone can lift up or quell 
its roaring waves. In vapor, how much variety is added 
to the view by the mist or the cloud, which, by their 
ever-changing shadows, diversify, at every movement, the 
landscape over which they are flitting ; whilst the gor- 
geous hues of the clouds around the setting sun, and 
the glowing tints of the rainbow, are due to the re- 
fractive action of water and watery vapor upon the solar 
rays." * 

NITROGEN. 

28. Preparation of Nitrogen. — Pure nitrogen may 
be readily prepared by passing a stream of chlorine gas 
through strong aqua ammonia. It is well to pass the 
nitrogen through a wash-bottle, to remove the white 
fumes, which, as we 'have seen (3), are a compound of 
hydrogen and nitrogen. The apparatus used is shown in 

* Miller's Elements of Chemistry, Part II. pp. 35, 36. 



23 



COMPOUNDS AND ELEMENTS. 



Figure 10. The chlorine is generated in the flask at the 
left ; the ammonia is put in the next bottle ; and the nitro- 

Fig. 10. 




gen is washed in the third bottle, by being made to bubble 
up through water. 

29. Properties of Nitrogeit. — Nitrogen is a colorless 
gas, and is a little lighter than air. Its chief characteris- 
tic is its inertness. We have already seen (3) that it 
neither burns nor allows a taper to burn in it. 

30. Nitric Oxide. — Put some bits of copper into a 
bottle (Figure 11), and add aquafortis or nitric acid. A 

Fig. 11. 







COMPOUNDS AND ELEMENTS. 23 

reddish gas fills the upper part of the bottle, and passes 
off through the tube. When collected over water, it is 
colorless. The red color was owing to impurities, which 
have been absorbed by the water. 

Invert a jar of this gas over a piece of well-lighted 
phosphorus, and the latter burns almost as brilliantly as 
in oxygen, filling the jar with white fumes of phosphoric 
a?ihydride {phosphoric acid.) The experiment proves 
the presence of oxygen in the gas in which the phosphorus 
was burned. 

Pass a mixture of equal parts of this same gas and 
hydrogen through a tube containing some heated platin- 
ized asbestos, and hold a piece of moistened red litmus- 
paper at the mouth of the tube. The paper is turned 
blue, showing that ammonia has been produced ; for am- 
monia is the only gas that turns red litmus-paper blue. 
We have seen (3) that ammonia is a compound of hy- 
drogen and nitrogen ; therefore there must have been 
nitrogen in the gas mixed with the hydrogen. 

The gas is, in fact, a compound of nitrogen and oxygen, 
and is called nitric oxide {deutoxide or binoxide of nitro- 
gen), and its symbol is NO. 

31. Catalysis. — In the above experiment the platin- 
ized asbestos remains wholly unchanged. By its mere 
presence, it has made the hydrogen unite with the ele- 
ments of the gas mixed with it. This remarkable action 
by mere presence is called catalysis. It occurs in many 
other cases, but is very imperfectly understood. 

32. Nascent State. — Nitrogen, as we have seen, is a 
very inert substance. Indeed, it can be made to com- 
bine directly with scarcely any element. In the above 
experiment, the hydrogen first seizes upon the oxygen, 
forming water, and sets the nitrogen free. At the mo- 
ment when it is thus set free it has an increased activity, 
and readily unites with the hydrogen to form ammonia. 



24 COMPOUNDS AND ELEMENTS. 

It is found generally true that elements are unusually- 
active when just liberated from compounds. They are 
then said to be in the nascent state. 

33. Nitrous Ait hydride. — If a jar of oxygen be in- 
verted over a jar of ?zitric oxide, the gases, on mixing, 
become of a bright cherry-red color. The compound 
formed differs from nitric oxide only in containing more 
oxygen. It is called nitrous anhydride {nitrous acid), 
and its formula is N 2 3 . 

34. Nitric Peroxide and Nitric Anhydride. — It is 
possible to form two higher oxides of nitrogen, NO s , 
nitric fer oxide, and N 2 5 , nitric anhydride. 

The former, at a temperature below Jo , is an orange- 
colored liquid ; and the latter is a white solid, which 
eagerly unites with -water, forming the well-known aqua- 
fortis, or nitric acid, HNO s . The reaction between 
nitric anhydride and water is shown by the following 
equation : — 

KH 2 + N 2 5 ) = HN0 8 . 

35. Nitric Acid. — Nitric acid is a strongly fuming 
liquid, colorless when pure, but usually yellowish from 
the presence of some of the lower oxides of nitrogen. 
It is one of the most corrosive substances known, and 
rapidly destroys all animal substances. When diluted, it 
stains the skin, wool, feathers, and the like, a bright yel- 
low color, and is often used as a permanent yellow dye 
for silk and woollen goods. It acts violently upon tin and 
iron filings, especially when they are moistened with 
water. Indeed it attacks all the ordinary metals, except 
gold and platinum. Its action upon them, however, is 
more energetic when it is somewhat dilute. 

The action of nitric acid upon the metals is owing to 
the readiness with which it parts with some of its oxy- 
gen. It first oxidizes them, and then acts upon these 



COMPOUNDS AND ELEMENTS. 2$ 

basic oxides (16), to form salts (17). During this pro- 
cess, the lower oxides of nitrogen are always given off, as 
is indicated by the appearance of red fumes. 

Nitric acid may be made on a small scale by heating 
potassic nitrate (saltpetre), in a retort with sulphuric 
acid (oil of vitriol). The nitric acid distils over, and is 
collected in a receiver. The re-action is as follows : — 

2KNO3 + H 2 S0 4 = K 2 S0 4 + 2HN0 3 . 

The hydrogen and the potassium change places, giving 
rise to potassic sulphate (sulphate of potash) and nitric 
acid. 

On the large scale, iron retorts, coated "with fire-clay on 
the inside of the upper part, where they are exposed to 
the acid vapors, are employed for the distillation, and 
sodic nitrate (soda saltpetre) is substituted for potassic 
nitrate, as it is a cheap sr salt, and likewise yields 9 per 
cent more nitric acid than potassic nitrate. 

30. Nitrous Oxide. — A fifth oxide of nitrogen is ob- 
tained by gently heating amnionic nitrate (nitrate of am- 
monia). It is called nitrous oxide, and its symbol is N 2 Q. 
The reaction is shown by the following equation : — 

(H 4 N)N0 3 = 2H 2 0+N 2 0. 

The amnionic nitrate, (H 4 N)N0 3 , breaks up into water 
and nitrous oxide. 

N 2 is a colorless gas, and readily gives up its oxygen. 
Phosphorus burns in it as brilliantly as in pure oxygen. 
A splint of wood "with a spark on the end of it bursts into 
flame when plunged into the gas. When inhaled, it has 
a peculiarly exhilarating effect, and hence is called laugh- 
ing gas. It is used by ^dentists as an ancesthetic, since it 
makes the patient for the time insensible to pain. Great 
care must be taken that the gas when inhaled is perfectly 
pure. 



26 



COMPOUNDS AND ELEMENTS. 



37. Ammonia. — We have seen (3) that ammonia is a 
compound of hydrogen and nitrogen. It is a colorless 
gas, which is greedily absorbed by water, forming the 
ordinary aqita ammonia. The eagerness with which it 
is taken up by water may be shown by filling a jar with 
the gas and opening it under water. The gas is instantly 
absorbed, and the water rushes in and fills the bottle. At 
a temperature of 32^, water will absorb more than one 
thousand times its bulk of ammonia. 

Ammonia takes its name from the fact that it was first 
obtained from a salt found in Libya, near the temple of 

Jupiter Ammon. It 
is now prepared from 
the same salt, sal-am- 
moniac or amnionic 
chloi'ide, which is 
made in large quan- 
tities from the waste 
liquor of gas-works. 
The sal-ammoniac is 
powdered and mixed 
with lime, and the 
mixture is heated in 
a flask arranged as 
shown -in Figure 12. 
The gas is washed by passing It through a wash-bottle, 
and is then conducted into water. 

38. Ammonium.- — The symbol of ammonic chloride 
is (H 4 N)C1; that of ammonic nitrate is (H 4 N)NO s . 
If we compare these with the symbols of the potassic 
chloride and nitrate, KC1 and KN0 3 , we shall see that 
the group of atoms H 4 N plays the same part in the com- 
pounds as the metal potassium ; and this is the case in 
a large class. of salts. Hence this group of atoms has 
come to be considered as a jnetal^ and has received the 




COMPOUNDS AND ELEMENTS. 2^ 

name of ammonium. It has not, however, been obtained 
in a separate form, since it at once breaks up into ammo- 
nia, H 3 N, and hydrogen. 

39. Cyanogen. — When carbon and nitrogen are heated 
together in the presence of potash, a remarkable com- 
pound called potassic cyanide {cyanide of potassium), 
KCN, is formed. From this a large number of substances 
can be prepared, all of which contain the group of atoms 

' CN. To this group the name cyanogen (blue-maker) is 
given, from its forming a number of blue compounds. It 
is remarkable as entering into composition exactly like a 
non-metallic element. It can be obtained in a free state 
as a colorless gas by heating mercuric cyanide (cyanide 
of mercury.) It forms with hydrogen an acid, HCN, 
analogous to muriatic acid, HC1. This acid is called 
hydrocyanic or prussic acid. 

The most important of the blue compounds of cyano- 
gen is Prussia?! blue, which may be formed by mixing 
a solution of either the red or the yellow prussiate of 
potash with a solution of green vitriol. 

Groups of atoms, like ELN and CN, which play the 
part of elements, are called radicals, 

40. Hie Characteristics of Nitrogen. — The most 
marked features of nitrogen are its i?zertness (29) ; the 
indirect way iit which it enters into combination; and 
the great variety, the reinarkable natitre, and the insta- 
bility of its compounds. 

The great variety of its compounds is shown in the 
five which it forms with oxygen : — 

Nitrous oxide, N 2 0. 

Nitric oxide, NO. 

Nitrous anhydride, N 2 O s . 
Nitric peroxide, N0 2 . 
Nitric anhydride, N 2 5 . 



2S COMPOUNDS AND ELEMENTS. 

These compounds, as we have seen, are widely unlike in 
their properties ; but in composition they differ only in the 
amount of oxygen which they contain. 

The remarkable nature of the compounds is illustrated 
by ammonium and cyanogen, one of -which acts like a 
metallic and the other as a noii-metallic element. 

The instability of the compounds is seen in the readi- 
ness with which the oxides give up their oxygen. Nitric 
iodide {iodide of nitrogen), which may be prepared by 
the action of ammonia on iodine, is so unstable that it 
explodes even when touched with a feather. Nitric 
chloride {chloride of nitrogen) is even more explosive, 
and is one of the most dangerous compounds known. 

CARBON. 

41. Properties of Carbon. — Carbon differs from the 
elements already described in being a solid when in a 
free state. It exists in three forms, which in outward 
appearance have nothing in common, but which are 
identical in their chemical relations. These three allo- 
tropic forms are diamond, graphite or plumbago, and 
charcoal. These differ in hardness, color, specific grav- 
ity, and the like ; but when burnt in oxygen, the same 
weight of each produces the same weight of carbonic 
acid. 

The diamond was first found to be pure carbon by 
Lavoisier in 177 '5~ 7°"- -^ occurs crystallized in certain 
rocks and gravels in India, Borneo, and Brazil. It is the 
hardest of all known bodies ; and when cut, has a brilliant 
lustre and a high refractive power. 

Graphite, plumbago, or black lead, is the substance 
used in the manufacture of the so-called " lead pencils." 
Although very brittle, its particles are very hard, so that 
a saw or other instrument used in cutting it is soon 
dulled. Mixed with oil it is extensively used to diminish 



COMPOUNDS AND EI EMENTS. 20, 

the friction of machinery. It is the basis of mcst kinds 
of stove-polish, and of certain paints used to protect iron- 
work. It is also made into crucibles, which, on account 
of their infusibility, are much prized by the chemist. 
Carbon, in all its forms, is the most infusible substance 
known. Its infusibility and its allotropic states are its 
chief characteristics. 

42. Carbonic Anhydride {Carbonic Acid). — The 
most important compound of carbon is C0 2 , carbonic 
anhydride, commonly called carbonic acid. This gas is 
readily prepared by the action of dilute muriatic acid on 

Fig- 13- 




chalk or marble (Figure 13). The reaction is as fol- 
lows : — 

CaCO s + 2HCI = CaCl 2 + H 2 -f C0 2 . 

CaC0 3 , calcic carbonate (chalk, or marble), is broken 
up by the action of the acid. The calcium combines 
with the chlorine of the acid, forming calcic chloride 
{chloride of calcium), CaCl 2 ; one atom of the oxygen 
combines with the hydrogen of the acid, forming water ; 
and C0 2 is set free. 

We have already seen (11) that lime-water readily 
shows the presence of carbonic acid, by becoming milky 
white." The lime-water contains lime, CaO, which com- 



30 COMPOUNDS AND ELEMENTS. 

bines with the carbonic acid, C0 2 , to form CaCO s 
again. 

If a lighted taper be plunged into a jar of carbonic 
acid, it goes out. We have seen that the same thing 
takes place in nitrogen ; but the two gases can be distin- 
guished by the lime-water test. 

Carbonic acid is about 1.5 times as heavy as air, so 
that, with an ordinary dipper, it can be dipped out from 
one jar and poured into another, lika water. It is poi- 
sonous when breathed, even though mixed with a large 
quantity of air. 

43. Cai'boitic Oxide. — Carbonic oxide, CO, is a gas 
formed when carbon burns with a limited supply of oxy- 
gen. It is often produced in an ordinary coal-fire, and is 
seen to burn with a pale blue flame. It is far more 
poisonous than carbonic acid. 

CO may be obtained pure from several compounds of 
carbon. Thus, if crystallized oxalic acid, C 2 H 2 4 , be 
heated with strong sulphuric acid, the latter withdraws 
from it one molecule of water, H 2 0, leaving C 2 3 , which 
at once splits up into CO and C0 2 . The C0 2 may be 
removed by passing the mixed gases through a solution 
of caustic soda. 

SULPHUR. 

44. Sources of Sulphur. — Sulphur occurs in nature 
both free and combined : it is found free in certain vol- 
canic countries, especially in Sicily and Iceland ; it exists 
in combination with many metals, forming sulphides. 
These sulphides are the ores from which several of the 
metals are commonly obtained. Thus PbS, plumbic 
sulphide (galena), ZnS, zincic sulphide (zinc blende), 
and CuS, cupric sulphide (sulphide of copper), are the 
most productive ores of those metals. 

In order to obtain pure sulphur, the mineral, containing 



COMPOUNDS AND ELEMENTS. 



3 1 



the crude substance mixed with earthy impurities, is 
heated in earthen pots (Figure 14) ; the sulphur distils 
over in the form of vapor, which is condensed in similar 
pots placed outside the furnace. The sulphur thus ob- 
tained is refined or purified by a second distillation. 

If the vapor of sulphur is quickly cooled below its 
melting-point, it solidifies in a crystalline powder, called 
flowers of sulphur ; just as watery vapor, when cooled 
below the freezing point of water, becomes snow. If 

Fig i4. 




sulphur is gently heated, it melts, and may be cast into 
sticks, and is then known as brimstone, or roll sulphur. 

45. Properties of Sulphur. — Sulphur is a yellow 
solid, and exists in three allotropic forms (iy). The 
first is that in which it crystallizes in nature. The other 
two are obtained by jnelting sulphur. If melted sulphur 
be allowed to cool slowly, it crystallizes in long, trans- 
parent needle-shaped crystals, which are quite different 
in form from the natural crystals, and have a specific 



32 COMPOUNDS AND ELEMENTS. 

gravity of 1.98, while the natural crystals have a specific 
gravity of 2.07. These transparent crystals become 
opaque after an exposure of a few days to the air, owing 
to their breaking up into several crystals of the natural 
and permanent form. The third allotropic form of sul- 
phur is obtained by pouring melted sulphur at 45 o° into 
cold water. It then forms a soft, tenacious mass, resem- 
bling india-rubber, and has a specific gravity of 1.96. 
This form of sulphur is not permanent. In a few hours 
it returns to its ordinary brittle state. These peculiar 
modifications are also apparent when sulphur is heated. 
It begins to melt at 239°, and forms an amber-colored 
limpid liquid ; as the temperature rises, it begins to 
thicken, and to become dark-colored, so that at about 
450° it can scarcely be poured from the vessel ; heated 
still higher, it again becomes fluid, and remains as a dark 
thin liquid, till the temperature rises to 836 , when it be- 
gins to boil, and gives off a red vapor. 

Sulphur is an inflammable substance, and when heated 
in the air or oxygen burns with a bluish flame, and with 
the suffocating odor so well known in the burning of a 
common lucifer match. It is insoluble in water and in 
most liquids, but dissolves in carbonic ui sulphide (50). 

46. Sulphurous JLizhydrzde {Sulphurous Acid). — 
This compound, S0 2 , as we have seen (11), is formed 
when sulphur is burned in oxygen, or in the air, which is 
a mixture of oxygen and other gases. The suffocating 
odor which we perceive when a common friction match 
is lighted is caused by S0 2 . 

The most important property of S0 2 is its power of 
bleaching silk, woollen, straw, etc. It is largely used for 
this purpose in the arts. 

This property may be illustrated by holding a red rose 
or other flower in a jar of S0 2 . The flower quickly 
loses its color. 



COMPOUNDS AND ELEMENTS. 33 

47. Sulphuric Acid. — Sulphuric acid, or oil of vit- 
riol, is the most important and most powerful of all the 
acids. It has a very strong attraction for water, and 
when the two are mixed, intense heat is developed. 
Hence caution is necessary in mixing them, especially in 
thick glass vessels. The acid should always be poured 
into the water, not the water into the acid. It rapidly 
chars all organic matter, and is a valuable drying agent. 

Sulphuric acid was first prepared by distilling green 
vitriol, or ferrous sulphate, whence its name, oil of 
vitriol. In this form it is sometimes known as Nord- 
hausen acid, from the name of the city in Saxony where 
it was first manufactured. It is a fuming liquid, denser 
than the ordinary acid, and is a mixture of this acid with 
the sulphuric anhydride. 

This method has long been superseded by a more con- 
venient one, which depends upon the fact that, though 
S0 2 does not combine with free oxygen and water to 
form sulphuric acid, it is capable of taking up the oxy- 
gen when the latter is united with nitrogen in the form 
of nitrous anhydride, N 2 3 . Thus : — 

SO, + H 2 + N 2 3 = H 2 S0 4 + 2NO. 

Sulphurous anhydride, water, and nitrous anhydride, 
yield sulphuric acid and nitric oxide. 

The NO formed in this decomposition takes up an- 
other atom of oxygen from the air, becoming N 2 3 , and 
this is again able to convert a second molecule of S0 2 , 
with water, H 2 0, into sulphuric acid, H 2 S0 4 ; being a 
second time reduced to NO, and ready again to take up an- 
other atom of oxygen from the air. Hence it is clear that 
the NO acts simply as a carrier of oxygen between the air 
and the S0 2 ; and a very small quantity of it is therefore 
able to convert a very large quantity of sulphurous an- 
hydride, water, and nitrous anhydride, into sulphuric acid. 

3 



34 COMPOUNDS AND ELEMENTS. 

This process is conducted on a large scale in chambers 
made of sheet-lead, which are often of a capacity of 
50,000 or 100,000 cubic feet. The sulphurous anhydride 
is obtained either by burning sulphur in a current of air, 
or by roasting a mineral called iron pyrites (ferric bi- 
sulphide, FeS 2 ), and is led, together with air, into the 
chamber. The N 2 3 is got from sodic nitrate (soda salt- 
petre), which is decomposed either by the heat of the 
burning sulphur, or in a separate furnace. Jets of steam 
are also blown into the chamber, and a thorough draft is 
maintained by a high chimney. The sulphuric acid, as 
it forms, falls to the floor of the chamber, whence it is 
continually drawn off. It is then heated, first in open 
leaden pans, and then in vessels of glass or platinum (as 
lead is attacked by the strong acid), until the excess of 
water is driven off, and a sufficiently concentrated acid is 
obtained. 

So extensively is this acid used, that the quantity 
manufactured in South Lancashire (England) alone ex- 
ceeds 3,000 tons a week. 

This method of making sulphuric acid may be illus- 
trated, on a small scale, by dipping a shaving or cloth in 
nitric acid, and then holding it in a jar of sulphurous 
anhydride, with a little water at the bottom of the jar. 
Red fumes at once appear, which show that the nitric 
acid has lost some of its oxygen, having given it up to 
the S0 2 , which thus becomes SO s . If the experiment be 
repeated a number of times, the water at the bottom of 
the jar will be found to contain sulphuric acid. 

48. Sulphuric Anhydride. — If fuming Nordhausen 
acid b^ gently heated in a glass retort, which is con- 
nected with a receiver, kept cool by ice, white fumes 
will pass over and solidify into a white silky fibrous 
mass. This solid is sulphzcric anhydride. It has no 
acid properties, and can be moulded in the fingers with- 



COMPOUNDS AND ELEMENTS. 35 

out charring the skin. When thrown on water, the heat 
emitted is so intense that it hisses like red-hot iron. 

49. Hydric Sulphide, Sulphuretted Hydrogen, or 
Hydrosidphuric Acid. — Sulphur combines with hydro- 
gen, forming hydric sulphide, H 2 S, a compound analo- 
gous in composition to water. It is a gas of a very 
offensive odor, and very poisonous. It reddens litmus- 
paper, and is therefore an acid. It is best prepared by 
the action of dilute sulphuric acid on ferrous sulphide, 
FeS. Thus: — 

FeS -f H 2 S0 4 == H 2 S + FeS<3 4 . 

The hydrogen and the iron change places, forming 
hydric sulphide and ferrous sulphate (sulphate of iron, 
or green vitriol). 

This gas is an invaluable agent in chemical analysis. 

50. Carbonic Disulphide. — If the vapor of sulphur 
be passed over red-hot charcoal, a volatile compound, 
CS 2 , is formed.- In is seen to be analogous to carbonic 
acid, C0 2 . It is a very inflammable, colorless liquid, of 
an offensive odor, and is called carbonic diszilphide (or 
bisulphide of carbon). It is of great importance in the 
arts, since it dissolves gums, caoutchouc, sulphur, and 
phosphorus. 

51. The Oxygen Group. — The two compounds, H 2 S 
and CS 2 , are analogous in composition to H 2 and C0 2 , 
and . it is true in general that for every oxide there is a 
corresponding sulphide. Thus we have K 2 0, potassic 
oxide (potassa), and K 2 S, potassic sulphide {sulphide 
of potassium) \ BaO, baric oxide (baryta), and BaS, 
baric sulphide {sulphide of barium) ; A1 2 3 , aluminic 
oxide {alumina), and A1 2 S 3 , aluminic sulphide {sul- 
phide of aluminium) ; and so on. 

Oxygen and sulphur, then, belong to the same group 
of elements, which may be called the oxyge?i group. To 



36 COMPOUNDS AND ELEMENTS. 

this group also belong the rare elements, selenium and 
telluriu?n. 

It will be noticed that the atomic weight of sulphur, 
32, is just double that of oxygen. 

CHLORINE. 

52. Preparation of Chlorine. — Chlorine, as we have 
already seen (1), is prepared by heating a mixture of 
muriatic acid and black oxide of manganese, Mn0 2 . 
The reaction is shown in the following equation : — 

Mn0 2 + 4HCI = MnCl 2 + 2 H 2 + 2CI. 

The hydrogen of the HC1 combines with the oxygen of 
the Mn0 2 , forming two molecules of water, 2H 2 0. 
Half the chlorine of the HC1 unites with the manganese, 
to form manga7tic chloride {chloride of manganese), 
MnCl 2 , and the other half is set free. 

53. Propei'ties of Chlorine. — Chlorine was dis- 
covered by Scheele in i774- -^ does not occur free in 
nature, but is found combined with metals, forming 
chlorides, of which rock-salt is the most common. 
Chlorine is, as we have seen, a greenish-yellow gas of a 
most disagreeable and irritating odor. It is very poison- 
ous when inhaled in any considerable quantity. It is a 
very heavy gas, being nearly 2.5 times as heavy as air. 
Chlorine has a very strong affinity for the metals. If 
these in a finely divided state are brought into contact 
with it, they take fire spontaneously, giving rise to me- 
tallic chlorides. It has so strong an affinity for phos- 
phorus, that this element will take fire spontaneously 
when put into a jar of chlorine. But the most remark- 
able property of chlorine is its power of combining with 
hydrogen to form muriatic acid. When these gases are 
mixed in equal volumes, they combine with an explosion 



COMPOUNDS AND ELEMENTS. 37 

on applying a lighted taper to them, or on exposing them 
to the sunlight. This property of chlorine has already 
been illustrated in the decomposition of water and am- 
monia (2, 3). 

Another remarkable property of chlorine is its bleach- 
ing power, which depends on its ability to decompose 
water. We may enclose a piece of cotton cloth colored 
with a vegetable substance in a bottle of dry chlorine, 
and no change of color takes place, even after many 
weeks. If, however, a few drops of water are added, 
the cotton is at once bleached. The chlorine, combines 
with the hydrogen of the water, and the oxygen, at the 
moment of its liberation, when it is in the nascent state 
(32), combines with the coloring matters, forming color- 
less compounds. Ordinary free oxvgen has not this 
power, at least to any great extent. 

54. Chloride of Lime, or Bleaching Powder. — Since 
chlorine destroys all organic colors (that is, all colors de- 
rived from the vegetable and animal kingdoms) it is very 
extensively used in bleaching cotton and linen goods and 
paper. Cotton fabrics may now be rendered perfectly 
white, in a few hours ; while, by the old method of lay- 
ing them on the grass in the sun, it required weeks, and 
even months, to effect it. It was necessary, moreover, 
to have meadow-land suitably situated for the bleaching ; 
hence most of the cloth manufactured in England was 
carried to Holland to be bleached. Besides the dimin- 
ished expense, the cotton stuffs bleached with chlorine 
suffer less injury in the hands of skilful workmen than 
those bleached in the sun. 

The health of the workmen is greatly endangered by 
the use of chlorine in the gaseous state ; but it has been 
found that the gas is readily absorbed by slaked lime, 
and is as readily given up again when the lime is treated 
with dilute acid. 



38 COMPOUNDS AND ELEMENTS. 

When thus combined with lime, the chlorine can be 
easily transported. The compound is called chloride of 
lime, or bleaching- powder. 

This powder is made on a large scale by conducting 
chlorine into spacious chambers, on the floor of which 
slaked lime is spread to the depth of two inches. 

In bleaching, the goods are first dipped into a solution 
of the bleaching powder, and then passed through dilute 
acid. The chlorine is thus set free in the fibres of the 
cloth, where it does its work of bleaching without injury 
to the workmen. 

Chloride of lime is also largely used as a disinfectant. 
The chlorine acts upon organic odors in the same way 
as upon organic colors ; that is, it oxidizes and destroys 
them. 

55. Hydric Chloride {Hydrochloric Acid). — Hydric 
chloride or hydrochloric acid is a colorless gas, some- 
what heavier than air, and is very soluble in water. This 
solution is the ordinary muriatic acid of the shops. It 
may be easily prepared, by placing in a capacious retort 
3 parts of fused sodic chloride (chloride of sodium, or com- 
mon salt) in fragments, and adding slowly, through a bent 
funnel, 3 parts of oil of vitriol. If pounded salt be used, 
the action of the acid is apt to be too rapid. The retort 
is connected with a series of bottles ; in the first, a small 
quantity of water is placed, to detain any impurities 
which might be carried over mechanically with the gas ; 
the second bottle may contain 4 parts of water, and 
should be immersed in a vessel of cold water, as the con- 
densation of the gas is attended with a great disengage- 
ment of heat. On applying a gentle heat to the retort, 
the acid comes over and is condensed ; an easily soluble 
sodic sulphate (sulphate of soda) remains in the" retort. 
For manufacturing purposes, the decomposition is effected 
in iron cylinders, like those employed in the manufacture 



COMPOUNDS AND ELEMENTS. 39 

of nitric acid, and only one half the quantity of sulphuric 
acid prescribed above is used : — 

2NaCl +H 2 S0 4 =:2HC1 +Na 2 S0 4 . 

Sodic sulphate, Na 2 S0 4 , remains in the cylinder, whilst 
the acid is condensed in a series of salt-glazed stone-ware 
jars. 

Enormous quantities of muriatic acid are obtained as an 
incidental product in the manufacture of soda-ash, which 
will be described farther on. More than iooo tons are 
made every week at the soda-ash works in South Lan- 
cashire (England) alone. 

56. Hydracids. — Hydric chloride, HO, and hydric 
sulphide, H 2 S, contain each but two elements, and no 
oxygen ; while nitric acid, HN0 3 , and sulphuric acid, 
H 2 S0 4 , contain each three elements, one of which is 
oxygen. There are, then, two classes of acids : one con- 
taining oxygen, and called oxy 'acids ; and the other, 
containing no oxygen, called hydracids. 

57. Aqua Regia. — When muriatic acid is mixed with 
nitric acid, it forms the so-called nitro-miwiatic acid. 
This acid was called aqua regia (royal water) by the 
alchemists, because it dissolves gold, the " king of 
metals." Both platinum and gold are insoluble in 
either acid separately ; but when the two acids are 
mixed, they decompose each other. Chlorine is set free, 
and in its nascent state (32) acts upon the metals, and 
dissolves them. 

58. Chlorine Oxy acids. — Chlorine has a very weak 
affinity for oxygen ; but it forms four oxyacids : hypo- 
chlorous acid, HCIO ; chlorous acid, HC10 2 ; chloric 
acid, HC10 3 ; and- ■ hyperchloric or perchloric acid, 
HC10 5 . Of these, the hypochlorous and the chloric 
form some important salts. 



4-0 COMPOUNDS AND ELEMENTS. 

BROMINE. 

59. Properties of Bromine. — This element, which 
closely resembles chlorine in its properties and com- 
pounds, was discovered by Balard, in 1826, in the salts 
obtained by the evaporation of sea-water. It does not 
occur free in nature, and is, like chlorine, found com- 
bined with sodium and magnesium as bromides in cer- 
tain mineral springs. 

Bromine is a dark, reddish-black, heavy liquid, being 
the only element, except mercury, that exists as a liquid 
at the ordinary temperature. Its specific gravity is 2.966, 
it freezes at — 9 , and boils at 145 . It has a very strong, 
irritating smell, resembling that of chlorine, and when 
inhaled, acts as a violent poison. It is quite soluble in 
water, and this solution bleaches, but more feebly than a 
solution of chlorine. Some of its salts are much used in 
medicine and in photography. 

IODINE. 

60. Properties of Iodine. — Iodine also occurs in sea- 
water, combined with sodium and magnesium. It was 
discovered in 181 2 by Courtois. At the ordinary tem- 
perature it is a dark gray solid, with a bright metallic 
lustre. It has a specific gravity of 4.95 ; it melts at 225 , 
and boils at about 350 . Its vapor is of a beautiful deep 
violet color, and has a faint chlorine-like smell. Iodine 
does not possess such active qualities as either chlorine 
or bromine. Its solution does not bleach vegetable colors, 
and it is set free from its compounds by both the above 
elements. Free iodine forms with starch a remarkable 
compound of a rich blue color (12). Iodine acts as a 
violent poison ; but, given in small quantities, it is much 
used as a medicine. Some" of its salts also are used in 
medicine and in photography. 



COMPOUNDS AND ELEMENTS. 



FLUORINE. 



4 1 



61. Properties of Fluorine. — This element occurs 
combined with the metal calcium, as calcic fluoride 
(fluoride of calcium) or flitor-spar. It is remarkable as 
forming no compound with oxygen, and as being ex- 
tremely difficult to prepare in a pure state. Many un- 
cuccessful attempts have been made to obtain fluorine ; 
but, by the action of dry iodine upon dry argentic fluoride 
(fluoride of silver), it appears to have been isolated ; and 
it-is found to be a colorless gas. 

62. Hydric Fluoride, or Hydrofluoric Acid. — When 
calcic fluoride (fluor spar) is acted upon by sulphuric 
acid, a very corrosive gas is obtained, called hydric 

fluoride {hydrofluoric acid). The reaction is shown in 
the following equation % — 

H 2 S0 4 + CaF 2 = CaS0 4 + 2HF. 

The calcium and the hydrogen change places, forming 
calcic sulphate {sulphate of lime), CaS0 4 , and hydric 
fluoride. 

This acid must be prepared in vessels of lead or plat- 
inum, since it rapidly attacks glass. It acts violently 
upon the skin, producing painful sores, and the fumes 
are very poisonous to the lungs. It is used for etching 
on glass. The glass is first covered with wax, through 
which the design is traced with a sharp point. The 
glass is then exposed to the gas, which corrodes it where 
the wax has been removed. The solution of the gas in 
water is also used for the same purpose. 

63. The Chlorine Group. — The four elements just 
described form a weli-marked group. They are espe- 
cially remarkable for their gradation of properties. Thus 
chlorine is a gas, bromine a liquid, and iodine a solid, at 
the ordinary temperature. Chlorine may be easily con- 



42 COMPOUNDS AND ELEMENTS. 

densed into a liquid, and the specific gravity of liquid 
chlorine is 1.33, of bromine 2.97, and of iodine 4.95. 
Liquid chlorine is transparent, bromine slightly so, and 
iodine opaque. The atomic weight and density of bro- 
mine are nearly the mean of those of chlorine and iodine, 

"X."" K I t 2*7 

^ ^ ' ^ = 81.25; and in its general chemical de- 
portment bromine stands half-way between the other 
two elements. 

These elements all form powerful acids with hydrogen, 
and have a strong affinity for the metals. They all have 
a very weak affinity for oxygen. 

PHOSPHORUS. 

64. Properties of Phosphorus. — This element does 
not occur free in nature, but is found combined with 
oxygen and calcium in large quantities in the bodies, 
especially the bones, of animals, and in the seeds of 
plants. Animals obtain their phosphorus from plants, 
plants from the soil, and the soil from the slow disin- 
tegration of the oldest rocks. Phosphorus was acci- 
dentally discovered by Brande, in 1669 ; but Scheele, 
in 1769, pointed out its existence in the bones, and 
carefully examined its properties. It is prepared from 
bones, and is used chiefly in the manufacture of lucifer 
matches. 

Phosphorus is a yellowish, semi-transparent solid, re- 
sembling wax. Its specific gravity is 1.83. It melts at 
in , and boils at 550 . In the air it gives off white 
fumes, and emits a pale light in the dark, whence its 
name, which means light-bearer. While emitting this 
light, it appears to be undergoing a slow burning. At a 
temperature a little above its melting-point, phosphorus 
takes fire in the air, and burns with great energy. It 



COMPOUNDS AND ELEMENTS. 43 

may be set on fire by slight friction, by a blow, and even 
by the heat of the hand. Hence it should be handled 
with great care, and always be cut under water. Phos- 
phorus has several well-marked allotropic states, the 
most important of which is that known as red phos- 
phorus. This is much less inflammable than ordinary 
phosphorus, and is not poisonous. 

65. Compounds of Phosphorus. — Phosphorus com- 
bines with oxygen, to form several acids, the most im- 
portant of which are known as hypophosphorous acid 
and phosphoric acid. From the former are derived salts 
{Jiypophosphites) , used in medicine ; while the latter fur- 
nishes a large class of salts {phosphates and superphos- 
phates), which are valuable to the farmer as fertilizers. 
Phosphorus unites with hydrogen, to form hydric phos- 
phide (phosphuretted hydrogen), H 3 P, a poisonous gas, 
with a very offensive odor. When this gas is prepared 
by the action of caustic potash on phosphorus, each 
bubble of the gas takes fire as it comes into contact with 
the air, forming beautiful rings of phosphoric anhydride 
(phosphoric acid), which expand as they rise. This 
spontaneous combustion is owing to the presence of a 
small quantity of a liquid compound of phosphorus and 
hydrogen, whose symbol is H 2 P. Pure phosphuretted 
hydrogen does not take fire in this way. 

ARSENIC. 

66. Properties of Arsenic. — Arsenic closely resem- 
bles phosphorus and nitrogen in its chemical properties, 
and in those of its compounds, and is therefore to be 
counted as a non-metallic element. In physical features, 
such as specific gravity and lustre, it bears a greater 
resemblance to the metals, with which it was formerly 
classed. (See, in Appendix, Chemical Philosophy, § 19.) 



44 COMPOUNDS AND ELEMENTS. 

Arsenic is sometimes found in a free state, but more 
often combined, chiefly with iron, nickel, cobalt, and 
sulphur. One of the compounds of this element with 
oxygen, As 2 3 , is the well-known poison, white arsenic. 

67. The Nitrogen Group. — Nitrogen, phosphorus, 
and arsenic form a well-marked group. They all form 
similar compounds with oxygen and with hydrogen. 
Thus we have H 3 N (ammonia), H 3 P (phosphuretted 
hydrogen), and H 3 As (hydric arsenide) ; N 2 8 (nitrous 
anhydride), N 2 5 (nitric anhydride), P 2 3 (phosphorous 
anhydride), P 2 O s (phosphoric anhydride), and As 2 3 
(arsenious anhydride), As 2 O s (arsenic anhydride). 

BORON. 

68. Prof erties of Boron. — Boron is found in nature 
combined with oxygen as boracic acid, and with oxygen 
and sodium as borax. In certain volcanic districts in 
Tuscany, jets of steam and gas are continually escaping 
from the earth. These steam-jets contain small quan- 
tities of boracic acid, which collects in artificial basins 
formed for the purpose at the mouth of the jet. By 
means of the heat of natural steam-jets, this solution of 
boracic acid is concentrated and crystallized. About 
2,000 tons of crude acid are thus prepared and exported 
from Tuscany every year. 

Boron is remarkable as combining directly with nitro- 
gen at a high temperature. 

SILICON. 

69. Properties of Silicon. — Next to oxygen, silicon 
is the most abundant element known. It does not, how- 
ever, occur in a free state, but always combined with 
oxygen (for which it has a very strong affinity) as silica. 



COMPOUNDS AND ELEMENTS. 45 

Silica is found nearly pure in quartz, flint, sand, and in 
several minerals, and combined with metals in almost all 
known rocks. Its symbol is Si0 2 . 

Silicon can be obtained in three modifications, corre- 
sponding to the three states of carbon. 

70. The Carbon Group. — Carbon and silicon, then, 
form a well-marked group, resembling each other closely 
in their allotropic states. 



SUMMARY. 

Chemistry divides substances into two classes : — 

1st, Elements, or substances which cannot be decom- 
posed by any known process. Of these only 65 are 
known. 

2d, Compounds, or substances made up of elements. 

The force which causes elements to combine, and 
holds them in combination, is called Ajfiitity. 

Affinity changes the properties of the substa?ices 
which it combiizes. 

Affinity always causes substances to combine in fxed 
and definite quantities. This law of combination is 
called the Law of Definite Proportions. 

A. given element combines with so?ne elemeizts in 
preference to others. 

Matter is made up of molecules ; and molecules are 
made up of atoms. 

The compounds of nitrogen and oxygen show that the 
same elements may combine in more than one propor- 
tion, and that in such cases the proportions of the ele- 
ments in the compounds are always multiples of the 
atomic weights of the elements. This law of combination 
is known as the Law of Multiple Proportions. 

The symbol of an element is usually the first letter of 
its name, a second letter being added to distinguish 



46 COMPOUNDS AND ELEMENTS. 

names beginning with the same letter. The symbol of 
an element always stands for one atom of the element. 

The symbol of a compound indicates its composition. 
It is formed by writing together the symbols of the ele- 
ments of the compound, with a small figure after each 
symbol expressing the number of atoms of that element 
found in a molecule of the compound. The symbol 
of a compound always stands for one 7nolecule of the 
compound. 

The chemical changes, or reactions, which substances 
undergo, are indicated by equations made up of these 
symbols. 

The compounds of oxygen with the elements are called 
oxides. These oxides are either acid, neutral, or basic. 
The oxides of the non-metallic elements are generally 
acid ; those of the metallic elements are generally basic. 

The acid oxides combined with water form acids. 

The basic oxides combined with water form bases. 

When a metal takes the place of the hydrogen of the 
acid, the compound is called a salt. 

A hydracid is made up of hydrogen and a non-metallic 
element. 

The names of binary salts take the ending -ide ; those 
of ternary salts, the endings -ate or -ite, according as the 
name of the acid ends in -ic or -ous. 

In general, the name of a binary compound takes the 
ending -ide. 

Oxygen is the most abundant element, and is usually 
prepared from potassic chlorate. It has a wider range 
of affinities than any other element. 

Ozone is an allotropic form of oxygen, and is more 
active than ordinary oxygen. 

Hydrogen is the lightest element, and is usually ob- 
tained by the action of zinc on dilute sulphuric acid. Its 
most important compound is water. 



COMPOUNDS AND ELEMENTS. tf 

Nitrogen is one of the most inert of elements. It is 
remarkable for the indirect way in which it enters into 
combination, and for the variety and the nature of its 
compounds. 

Carbon is an infusible solid, and has three allotropic 
states. 

Sulphur is an inflammable solid, forming sulphides 
which in their composition resemble oxides. It has 
several remarkable allotropic states. 

Chlorine is most readily prepared by the action of 
black oxide of manganese on muriatic acid. It is distin- 
guished by its color, its odor, and its affinity for hydrogen 
and the metals. Its bleaching and disinfecting power is 
due to its strong affinity for hydrogen. 

Bromine, iodine, and Jluorine are elements closely re- 
sembling chlorine in their chemical properties. 

Phosphorus is a very inflammable substance, and is 
mainly used for making lucifer matches. It is obtained 
from bones. 

Phosphorus and arsenic resemble nitrogen in the com- 
pounds which they form. 

Silicon resembles carbon in its allotropic states. 

Borcn combines directly with nitrogen at a high tem- 
perature. 

Nitric acid is remarkable for its oxidizing power. 

Sulphuric acid is the strongest of acids, and is re- 
markable for its affinity for water. 

Sulphurous acid is a bleaching agent. 

Nitrous oxide is used as an anaesthetic. 

Carbonic acid is a heavy gas, and is most readily pre- 
pared by the action of muriatic acid on marble. 

The most important non-metallic sulphides are hydric 
stdphide and carbonic bisulphide. 

The most important of the non-metallic chlorides is 
muriatic acid. 



48 COMPOUNDS AND ELEMENTS. 

Cyanogen is a remarkable compound of nitrogen 
and carbon, and plays the part of a non-metallic 
element. 

Ammonium is a remarkable compound of nitrogen and 
hydrogen, and plays the part of a metal. 

Ammonia, although it is not an oxide, has very pow- 
erful basic properties. It is known as the volatile alkali . 
and is extensively used in the arts. 



THE METALS. 



GENERAL PROPERTIES OF THE METALS. 

71. Physical Properties of the Metals. — The metals 
differ widely from one another, both in their physical and 
chemical properties. Those metals which are lightest 
have the greatest affinity for oxygen, whilst the heavier 
metals are oxidized with difficulty. 

The following Table gives the specific gravities of the 
most important metals : — 



Iridium 


21.8 


Iron 


7.8 


Platinum 


21.5 


Tin 


7-3 


Gold 


19-3 


Zinc 


7-i 


Mercury 


13.596 


Antimony * 


6. 7 


Lead 


"•3 


Chromium 


5-9 


Silver 


10.^ 


Aluminium 


2.56 


Bismuth * 


9.8 


Strontium 


2 -54 


Copper 


8. 9 


Magnesium 


*-75 


Nickel 


8.8 


Calcium 


1.5S 


Cadmium 


8.6 


Sodium 


0.972 


Cobalt 


8.5 


Potassium 


0.865 


Manganese 


8.0 


Lithium 


°-593 



The melting-points of the metals differ even more 
widely than their densities, as will appear from the fol- 
lowing Table, which is mainly compiled from Miller : — 



* In their chemical properties, bismuth and antimony appear 
to be non-metals. See § 99. p. 73. 



5° 


THE METALS. 






Mercury 
Cadmium 
Tin 
Bismutli 


— 39° 

+242 

442 
507 


Antimony 
Silver 
Copper 
Gold 




+ 737 c 
iS73 
1996 

2016 


Lead 
Zinc 


617 
733 


Steel 
Wrought Iron 


2 35o 
2700 


to 2500 
to 2850 



Some metals can be easily converted into vapor, or 
volatilized ; thus mercury boils at 662° , while potassium, 
sodium, magnesium, zinc, and cadmium can be distilled 
at a red heat. Even the more infusible metals, such as 
copper and gold, are not absolutely fixed, but give off 
small quantities of vapor when strongly heated. 

72. Metallic Ores. — Only a few of the metals occur 
in a free state in nature ; in general they are found com- 
bined with oxygen, sulphur, or some other non-metal. 
These metallic compounds are most variously distributed 
throughout the earth's crust ; some are known to occur in 
only one or two localities, and even then only in minute 
quantity, while others are found widely distributed in 
enormous masses. Aluminium, iron, calcium, magne- 
sium, and sodium form,' when united with oxygen and 
silicon, the whole mass of granitic rocks composing our 
globe ; but it is not from these sources that they can be 
obtained for the purposes of the arts. For this object we 
employ other combinations, found in smaller quantity, 
termed metallic ores, from which the metals can be more 
easily extracted. 

The heavy metals and their ores are interspersed 
throughout the older rocks, in the form of veiizs or lodes, 
which are cracks or fissures of the rock filled up with 
the ore. Other ores, such as ironstone, are found in the 
more recent rocky formations, having been deposited in 
large masses, probably from aqueous solution. 



THE METALS. 5 1 



THE MOST USEFUL METALS. 

The most useful metals are iron, lead, copper, tin, and 
zinc. 

73. IRON. — Iron is, of all metals, the most important 
to mankind. Its uses were long unknown to the human 
race, the age of iron implements being preceded by the 
ages of bronze and stone. Pure metallic iron exists only 
in very small quantity on the earth's surface, almost en- 
tirely occurring in meteoric stones. 

The process of obtaining iron from its ores requires an 
amount of knowledge and skill which the early races of 
men did not possess. The iron of commerce exists in 
three different forms, exhibiting very different properties, 
and having different chemical constitutions : (i) wrought 
iron; (2) cast-iron; (3) steel. 

The first is nearly pure iron ; the second is a compound 
of iron with varying quantities of carbon and silicon ; and 
the third a compound of iron with less carbon than is 
needed to form cast-iron. 

Pure iron in the form of powder may be obtained by 
heating the oxide moderately in a current of hydrogen. 
The hydrogen combines with the oxygen to form water, 
leaving the iron free. It must, however, be kept in an 
atmosphere of hydrogen, as finely divided iron takes fire 
spontaneously in the air. Iron has a bright white color, 
and is remarkably tough, though soft. The pure metal 
crystallizes in cubes. Iron which has been hammered 
has, when broken, a granular structure ; but it becomes 
fibrous when the iron is rolled into bars, and the more or 
less perfect form of the fibre determines to a great extent 
the toughness and the value of the metal. This fibrous 
texture of hammered bar-iron undergoes a change when 



5 3 THE METALS. 

exposed to long continued vibration, the iron returning to 
its original crystalline condition. Many accidents have 
occurred in the breaking of railway axles, owing to 
this change from the fibrous to the granular texture. 
Wrought iron melts at a very high temperature ; but, as 
it becomes soft at a much lower point, it can be easily 
worked. When hot, it possesses the peculiar property of 
welding ; that is, the power of uniting firmly when two 
clean surfaces of hot metal are hammered together. 

Iron and certain of its compounds are strongly mag- 
netic. The metal loses this power when red-hot, but 
regains it upon cooling. A solid mass of iron does not 
oxidize or tarnish in dry air, at the ordinary temperature ; 
but if heated, it oxidizes in black scales. When more 
strongly heated in the air, or plunged into oxygen gas, it 
burns with the formation of the same black oxide (n). 
In pure water, iron does not lose its brilliancy ; but, if a 
trace of carbonic acid is present, and access of air is per- 
mitted, the iron soon rusts. 

74. Manufacture of Iron. — The oldest method of 
manufacturing wrought iron was to heat the ore in a blast- 
furnace with charcoal or coal, and to hammer out the 
spongy mass of iron thus obtained. This plan can only 
be economically followed on a small scale and with the 
purest ores, and has been superseded by a more compli- 
cated method, applicable to all kinds of iron-ore. The 
most important ore is an impure carbonate called clay 
ironsto7te. This is first roasted (that is, heated in con- 
tact with air) to drive off the carbonic acid, and reduce 
the iron to an oxide. It is next smelted in a blastfur- 
nace. These furnaces (Figure 15) are usually about 
fifty feet high, and about fifteen feet in diameter in the 
widest part of the cavity CD. The lowest part, F, is 
called the crucible, or hearth. I Z are the tuyeres, or 
pipes through which air is forced by powerful bellows. 



THE METALS. 



53 



K, K, and M are arched galleries for the convenience 
of workmen employed about the furnace. When 
working regularly, the 
furnace is charged from 
a door at the end of the 
gallery near the top, first 
with cbal, and then with 
a mixture of roasted ore 
and limestone broken 
into small pieces. As 
the fuel burns away and 
the materials gradually 
sink, fresh supplies of 
fuel and of ore arc add- 
ed ; so that the furnace 
is kept filled with alter- 
nate layers of each. 

The oxygen of the air 
from the bellows com- 
bines with the carbon of 
the fuel, forming car- 
bonic oxide, CO, which 

rises through the porous mass, and, taking the oxygen 
from the ore, becomes converted into carbonic acid, C0 2 . 
The iron, mixed with the earthy matter of the ore, settles 
down into the hottest part of the furnace, where both are 
melted. The iron, being the heavier, sinks to the bot- 
tom, where it is drawn off at intervals through a tap-hole 
in the floor H. The lighter earthy matter, or slag, floats 
on the surface of the iron, like oil on w r ater, and flows off 
through an opening above the tymfi-stone L. The lime- 
stone aids in liquefying the earthy matter, and unites with 
it to form the slag. 

At this stage the iron is cast-iron. 

The properties and appearance of cast-iron vary much 




54 



THE METALS. 



with the amount of carbon and silicon which it contains ; 
for cast-iron is not a definite chemical compound of these 
elements with iron. The carbon is found in cast-iron, 
(i) as scales of graphite, giving rise to mottled cast-iron ; 
and (2) in combination, forming white cast-iron. 

In order to make wrought iron from cast-iron, the latter 
must undergo the processes of refining and fuddling. 
These consist essentially in burning out the carbon and 
silicon, by exposing the heated metal to a current of air 
in a reverberatory furnace. Such a furnace is repre- 

Fig. 16. 




sented in Figure 16. The ore is put into the hoppers 
H H, from which it falls into the chamber C, where it is 
spread out on the bed c c. The fuel is burned on a 
hearth at A, separated from the ore by the bridge b. 
The heated gases rising from the burning fuel are rever- 
berated, or reflected, by the arched roof of the furnace, 
and driven down upon the ore, and then pass off through 
the fluey*. When the ore is sufficiently roasted, it is 
allowed to fall through openings, d d, into the cham- 
ber E. The ore is stirred from time to time, to expose 
fresh surfaces to the action of the air and the flame. The 
melted cast-iron becomes first covered with a coat of 
oxide, and gradually thickens, so as to allow of its being 
rolled into large lumps or balls. During this process, the 



THE METALS. 



55 



whole of the carbon escapes as carbonic oxide, and the 
silicon becomes oxidized to silica, which unites with the 
oxide of iron, and forms a fusible slag. Any phosphorus 
or sulphur contained in the iron is also oxidized in this 
process. The ball is then hammered, to give the metal 
coherence, and to squeeze out the liquid slag, and the 
mass is afterwards rolled into bars or plates. 

75. Steel. — Steel is formed when bars of wrought 
iron are heated to redness for some time in contact with 
charcoal. The bar is then found to have become fine- 
grained instead of fibrous ; the substance is more mal- 
leable and more easily fusible than the original bar-iron, 
and is found to contain carbon varying in amount from 
one to two per cent. Steel has several important prop- 
erties, especially the power of becoming very hard and 
elastic when quickly cooled, which fits it for the manu- 
facture of edge-tools. These are, however, generally 
made of bar-steel, which has been previously fused and 
cast into ingots. 

A new and very rapid mode of preparing cast-steel is 
that known as the Bessemer process. This process con- 
sists in burning out all the carbon and silicon in cast-iron, 
by passing a blast of atmospheric air through the molten 
metal, and then adding such a quantity of pure cast-iron 
to the wrought iron thus prepared as is necessary to give 
carbon enough to convert the whole mass into steel. 
The melted steel is then at once cast into ingots. In this 
way six tons of cast-iron can, at one operation, be con- 
verted into steel in twenty minutes. The Bessemer steel 
is now largely manufactured for railway axles and rails, 
for boiler-plates, and other purposes, for which it is much 
better fitted than wrought iron, so that this process bids 
fair to revolutionize the old iron industry. It has already 
been put into practice on a large scale in England, France, 
Belgium, Sweden, and India. 



5*> THE METALS. 

76. LEAD. — Lead does not occur free in nature. It 
is obtained from galena, or plumbic sulphide, PbS. The 
galena is roasted in a reverberatory furnace, with the 
addition of a small quantity of lime to form a fusible slag 
with any silicious mineral matter present in the ore. By 
the action of the air, a portion of the sulphide is oxidized 
to sulphate, while in another portion the sulphur burns 
off, and plumbic oxide is left behind. After a time, the 
air is excluded, and the heat of the furnace raised, and 
the remaining sulphur burns at the expense of the oxygen 
in the oxide already formed, leaving the lead free. 

Lead is a bluish-white metal, and so soft that it may 
be scratched with the nail. It is quite ductile and malle- 
able, but has little tenacity or elasticity. It melts at 617 \ 
and at a higher temperature volatilizes, though not in 
quantity sufficient to be distilled. 

The surface of the metal remains bright in dry air, but 
it soon becomes tarnished in moist air, owing to the 
formation of a film of oxide ; and this oxidation j:>roceeds 
rapidly in presence of a small quantity of weak acid, such 
as carbonic or acetic. In pure water freed from air, lead 
also preserves its lustre ; but, if air be present, plumbic 
oxide is formed, and as this dissolves slowly in the water, 
a fresh portion of metal is exposed for oxidation. This 
solvent action of water upon lead is a matter of much 
importance, owing to the common use of lead water- 
pipes, and the peculiarly poisonous action of lead com- 
pounds upon the system -when taken even in minute 
quantities for a length of time. The small quantity of cer- 
tain salts contained in all spring and river waters exerts 
an important influence on the action of lead. Thus 
waters containing nitrates or chlorides are liable to con- 
tamination with lead, while those hard waters contain- 
ing sulphates or carbonates may generally be brought 
into contact with lead without danger, as a thin deposit 



THE METALS. 57 

of sulphate or carbonate is formed, which preserves the 
metal from further action. If the water contains much 
free carbonic acid, it should not be allowed to come into 
contact with lead, as the carbonate dissolves in water 
containing this substance. The presence of lead in 
water may easily be demonstrated by acidulating the 
water, passing a current of hydric sulphide (sulphuretted 
hydrogen) through a deep column of the liquid, and 
noticing whether it becomes tinged of a brown color, 
from the formation of plumbic sulphide. 

Lead pipes lined with tin have been recommended for 
water-pipes ; but if the lining is not absolutely perfect, 
they are more dangerous than ordinary lead pipes. If 
from defective soldering, or cracks, or breaks in the lin- 
ing, or from corrosive action, the water comes in contact 
with the lead, a galvanic action begins, and the lead is 
more rapidly oxidized than it would be if not joined with 
the tin. 

There is the same danger in the use of the metallic 
double-lined ice-pitchers. The lining is often made of 
dissimilar metals, and the parts are joined by a solder 
containing lead. The thin film of silver is soon worn 
off upon the interior ; galvanic action then promotes 
corrosive action, and the water becomes poisonous. 

On the whole, the best way of protecting lead-pipes 
from oxidation, is by coating them with sulphide of lead, 
which is insoluble in water. This can be done by dis- 
solving one pound of potassic sulphide (sulphide of 
potassium) in two gallons of water, and letting the 
solution remain in the pipe twelve hours, or until the 
whole inside is thoroughly blackened. This preventive 
process is not perfect, but it is very nearly so. 

77. COPPER. — Copper is an important metal, 
largely used in the arts. It has been known from very 



$8 THE METALS. 

early times, as it occurs native in the metallic state, and 
is moreover easily reduced from its ores. Metallic cop- 
per is found in enormous quantity near Lake Superior, in 
North America, and other localities. The following ores 
are the most important: (i) a compound of copper, sul- 
phur, and iron, known as copper pyrites, Cu 2 S -|- Fe 2 S 3 ; 
(2) the cuprous sulphide, Cu 2 S ; (3) the carbonate or 
malachite; and (4) the red or cuprous oxide, Cu 2 0. 
Copper is obtained on a large scale from the carbonate 
or oxide, by reducing these ores, together with carbon 
and some silica, in a blast-furnace. 

Metallic copper has a peculiar deep red color, which 
is best seen when a ray of light is several times reflected 
from a bright surface of the metal ; it is very malleable, 
ductile, and tenacious ; it melts at a red heat, and is 
slightly volatile at a white heat, giving a green tint to a 
flame of hydrogen gas which is passed over it ; and it is 
one of the best conductors of heat and electricity. Cop- 
per does not oxidize, either in pure dry or moist air, at 
ordinary temperatures, but if heated to redness in the air, 
it is soon converted into cupric oxide. 

78. Alloys of Copper. — Copper combines with several 
of the metals to form what are called alloys. 

Brass is an alloy containing about two-thirds of copper 
and one-third of zinc. It is harder than copper, and can 
be more easily worked. The addition of from one to 
two per cent of lead improves the quality of brass for 
most purposes. The yellow metal, used for the sheath- 
ing of ships, contains sixty per cent of copper. Bronze, 
gun-metal, bell-metal, and speculum-metal are alloys 
of copper and tin in varying quantities. They are all 
remarkable for the property of being hard and brittle 
when slowly cooled, but of becoming soft and malleable 
if, when red-hot, they are cooled suddenly by dipping 
into cold water. 



THE METALS. 



59 



79. TIN. — The ores of tin — although this metal has 
been known from very early times — occur in but few 
localities, and the metallic tin is not found in nature. 
The chief European sources of tin are the Cornish mines, 
where it is found as tin-stone, Sn0 2 . It was probably 
from these mines that the Phoenicians and Romans ob- 
tained all the tin which they employed in the manufac- 
ture of bronze. Tin-stone re also met with in Malacca 
and Borneo and Mexico. In order to prepare the metal, 
the tin-stone is crushed and washed to remove mechani- 
cally the lighter portions of rock with which it is mixed, 
and the purified ore is then placed in a reverberatory 
furnace, with anthracite or charcoal, and a small quantity 
of lime. The oxide is thus reduced, and the liquid 
metal, together with the slag, consisting of calcic silicate, 
falls to the lower part of the furnace. The blocks of tin, 
still impure, are then refined by gradually melting out 
the pure tin, leaving an impure alloy behind. 

Tin has a white color resembling that of silver ; it is 
soft, malleable, and ductile, but has little tenacity. When 
bent, pure tin emits a peculiar crackling sound. It melts 
at 442 \ and is not sensibly volatile. Tin does not lose 
its lustre on exposure to the air, whether dry or moist, at 
ordinary temperatures ; but if strongly heated, it takes 
fire, and a white powder of stannic oxide is formed. 

Owing to its brilliancy, and its power of resisting 
ordinary atmospheric changes, tin is largely used for 
coating iron, copper, and other metals, which are more 
abundant and more easily oxidized. Tin plate, or sheet 
tin, as it is called, is iron thus coated with tin. The thin 
sheets of iron are thoroughly cleaned with sulphuric acid, 
and then immersed in melted tin for an hour or so. 
Copper is tinned by brushing the melted tin over its sur- 
face, which must first be made perfectly clean. 

Tin is sometimes used for water-pipes ; and there is a 



OO THE METALS. 

popular impression that it is never acted upon by water. 
In certain localities, however, it oxidizes rapidly, and is 
soon rendered worthless. The safety of tin pipes, as 
compared with lead, does not consist in their exemption 
from corrosive action, but in the harmlessness of the re- 
sultant oxides and carbonates. 

80. Alloys of Tin. — Several alloys of tin, besides those 
already mentioned (78), are employed in the arts. Bri- 
tannia metal is an alloy of equal parts of brass, tin, 
antimony, and bismuth. The best pewter is an alloy of 
four parts of tin to one of lead. Common solder con- 
tains equal parts of tin and lead, and is more fusible 
than lead. 

81. ZINC. — Zinc is an abundant and useful metal, 
closely resembling magnesium in its chemical character, 
but it is much more easily extracted from its ores. The 
chief ores of zinc are the sulphide or blende, the ca?'- 
bonate or cala,mine, and the red oxide. In order to 
extract the metal, the powdered ore is roasted, to convert 
the sulphide or carbonate into oxide ; the roasted ore is 
then mixed with fine coal or charcoal, and strongly 
heated in crucibles or retorts of peculiar shape ; the 
zincic oxide is reduced by the carbon, carbonic oxide 
gas comes off, and the metallic zinc distils over, and is 
easily condensed. 

Zinc is a bluish-white metal, with a crystalline struc- 
ture. It is brittle at the ordinary temperature, but when 
heated to between 200° and 300°, it may be rolled out or 
hammered with ease. If more strongly heated, it is 
again brittle, and may be broken up in a mortar. Zinc 
melts at 773 , and at a bright red heat it begins to boil, 
and volatilizes ; or if air be present, it takes fire, and 
burns with a greenish flame, forming zincic oxide. Zinc 
is not acted upon by moist or dry air, and hence it is 



THE METALS. 6l 

largely used in the form of sheets, and is employed as a 
protecting covering for iron. The sheets of iron are 
plunged into melted zinc, covered with sal-ammoniac, 
which keeps the surface of the zinc free from oxide, and 
allows the two metals to unite. Iron thus coated with 
zinc is said to be galvanized. German silver is an 
alloy of zinc, copper, and nickel. 

82. IRON SALTS. — The oxides of iron are four in 
number: (1) ferrous oxide, FeO, from which the green 
or ferrous salts are derived ; (2) ferric oxide, Fe 2 3 , 
yielding the yellow ferric salts ; (3) the magnetic, or 
black oxide, Fe 3 4 , which does not form any definite 
salts ; (4) ferric acid, H 2 Fe0 4 , a weak acid, forming 
colored salts with potassium. The ferrous oxide colors 
glass green, and gives the peculiar tint to common bottle- 
glass. The most important of the ferrous salts are, — 

(1) Ferrous Sulphate, FeS0 4 . This soluble salt, 
sometimes called green vitriol, is obtained by dissolving 
(1) metallic iron, or (2) ferrous sulphide, in sulphuric 
acid, or by the slow oxidation of iron pyrites, FeS 2 . 

( X ) Fe + H 2 S0 4 = FeS0 4 +H a . 

(2) FeS + H 2 S0 4 = FcS0 4 + H 2 S. 

The solution thus obtained yields, on evaporation, large 
green crystals of the salt. It is largely used in the 
manufacture of several black dyes, and is one of the 
constituents of writing ink. Like ferrous oxide, this 
salt easily takes up oxygen, producing a new salt called 
ferric sulphate. 

(2) Ferrous acetate, formed by the action of acetic 
acid on iron, is largely used in dyeing and calico-print- 
ing. 

Of the ferric salts, the chloride, Fe 2 Cl 6 , is the most 



62 THE METALS. 

important ; it forms in brilliant red crystals when chlo- 
rine gas is passed over heated metallic iron. 

83. LEAD SALTS. — Three compounds of lead 
and O are known: (1) Litharge, ox plumb otis oxide, 
PbO, a straw-colored powder obtained by heating lead 
in a current of air. It is used in painting and in glass- 
making, and with acids forms the important lead salts. 
(2) Plitmbic oxide, Pb0 2 . (3) Red oxide, or red lead, 
a compound of the two last oxides, having the composi- 
tion, 2 PbO, Pb0 2 . It is obtained by exposing litharge 
to the air at a moderate red heat, oxygen being absorbed. 
Red lead is used as a paint and in glass-making. 

Of the soluble salts of lead, the nitrate, Pb2N0 3 , is the 
most important. This compound is obtained by dissolv- 
ing the oxide, the carbonate, or metallic lead in warm 
nitric acid. Plumbic acetate, or sugar of lead, is also a 
soluble salt. Almost all the other lead salts are insoluble 
in water. Plumbic cai'bonate, or white lead, PbCO s , is 
a substance much used in the arts as a paint. The salt 
may be obtained in the pure state by precipitating a cold 
solution of the nitrate with an alkaline carbonate, when 
it falls down as a white powder. For preparing the salt 
in quantity, two plans are employed : the one similar in 
principle to that described for the pure salt ; and the 
other an old and interesting process, known as the Dutch 
method. In this process thin sheets of lead are rolled 
into a coil, and each coil placed in an earthen pot con- 
taining a small quantity of crude vinegar, which, how- 
ever, does not come in contact with the lead. Several 
hundred of these jars and coils are packed on a floor in a 
bed of stable manure or spent tan-bark, and then cov- 
ered with boards, while a second layer of pots similarly 
charged is placed above, and this is continued until the 
building is filled. After remaining thus for several weeks, 



THE METALS. 63 

the coils are taken out, when the greater part of the lead 
is found to be converted into white carbonate. It appears 
that a lead acetate is first formed, and that the acetic acid 
is gradually driven out from its combination by the car- 
bonic acid evolved from the putrefying organic matter, 
and thus enabled to unite with another portion of the lead 
lying underneath that which was first attacked. 

Plumbic sulphide, or galejza, PbS, is found native, and 
is the chief ore of the metal. It is prepared as a black 
precipitate by passing sulphuretted hydrogen gas through 
a solution of a lead salt. Galena has a bright bluish-white 
metallic lustre. Plumbic sulphate PbS0 4 , is a white in- 
soluble salt, which is found native, and is prepared artifi- 
cially by adding sulphuric acid to a soluble lead salt. 
Plumbic chloride, PbCl 2 , is prepared by adding muriatic 
acid to a strong solution of plumbic nitrate, when a crys- 
talline precipitate of plumbic chloride is formed. It dis- 
solves in about thirty parts of boiling water, separating 
out in shining needles on cooling. Plumbic iodide, Pbl 2 , 
is precipitated in the form of splendid yellow spangles, 
when hot solutions of potassic iodide and plumbic ni- 
trate are mixed and allowed to cool. Plumbic chromaie, 
PbCr0 4 , is a yellow insoluble salt, generally known as 
chrome yellow, and much used as a paint. 

84. COPPER SALTS. — Copper forms two oxides, 
cuprous oxide, Cu a O, and cupric oxide, CuO. Cuprous 
oxide imparts to glass a ruby color. Cupric oxide is sol- 
uble in acids, and forms a series of salts. The most im- 
portant of the soluble salts are cupric sulphate, CuS0 4 , 
and cupric acetate, or verdigris. The former is often 
called blue vitriol, and is largely manufactured by dis- 
solving copper or its oxide in sulphuric acid. It is used 
in calico-printing, and in making Scheele' 's green, or cu- 
pric arseniate, and other paints. 



64 THE METALS. 

As many of the vegetable acids act upon copper so as 
to form poisonous salts, copper or brass vessels should 
never be used for cooking unless they are lined with tin. 

85. SALTS OF ZINC — Zinc forms but one ox- 
ide, ZnO, which is much used as a white paint. Its 
most important salt is zincic sulphate, or white vitriol, 
which is used in calico-printing. 

86. SAL TS OF TIN — Tin forms two oxides, the 
stannous, S11O, and the stannic, Sn0 2 . Stannous chlo- 
ride, SnCl 2 , formed by dissolving tin in muriatic acid, is 
termed tin salts in commerce ; it is largely manufactured 
for the calico-printer and dyer, who use it as a mordant ; 
that is, to Jix the color in the fibre of the cloth, so that it 
will not wash out. Potassic st annate {st annate of pot- 
ash), K 2 Sn0 3 , formed by boiling stannic oxide with soda, 
is used in the same way. Stannic chloride, SnCl 4 , is 
also used by dyers, and is prepared for this purpose by 
dissolving tin in cold nitro-muriatic acid. Of the sul- 
phides of tin, SnS, stannous sulphide, and SnS 2 , stannic 
sulphide, are the most important ; the former is blackish- 
gray, and the latter a bright yellow crystalline powder, 
known as mosaic gold, 

NOBLE METALS. 

The noble metals are mercury, silver, gold, and plati- 
num. They are so called because they do not rust, that 
is, combine with the oxygen of the air at ordinary tem- 
peratures. 

87. MER CURT. — The chief ore of mercury is the 
sulphide, or cinnabar, which occurs at Almaden in Spain, 
at Idria in Illyria, in California, and also in China and 



THE METALS. 65 

Japan. The metal is easily obtained by roasting the ore, 
when the sulphur burns off, and the metal volatilizes, and 
its vapor is condensed in earthen pipes. Mercury is the 
only metal liquid at the ordinary temperature ; it freezes 
at — 39 ; in the solid state it is malleable and possesses 
a density of 14.4. It boils at 662 , and gives off a slight 
amount of vapor at the ordinary temperature. Mercury, 
when pure, does not tarnish in moist or dry air ; but when 
heated above 700 , it rapidly absorbs oxygen ; and it 
combines directly with chlorine, bromine, iodine, and 
sulphur. Mercury is largely used in extracting gold and 
silver from their ores, and for many other purposes. 

Mercury dissolves many of the metals, forming amal- 
gams. The most important of these is the amalgam of 
tin and mercury, used for silvering mirrors. " In order 
to apply it to the glass, a sheet of tinfoil is spread evenly 
upon a smooth slab of stone, which forms the top of a 
table carefully levelled, and surrounded by a groove, for 
the reception of the superfluous mercury. Clean mercury 
is poured upon the tinfoil, and spread uniformly over it 
with a roll of flannel ; more mercury is then poured on 
till it forms a fluid layer of the thickness of about half a 
crown ; the surface is cleared of impurities by passing a 
linen cloth lightly over it ; the plate of glass is carefully 
dried, and its edge being made to dip below the surface 
of the mercury, is pushed forward cautiously ; all bubbles 
of air are thus excluded as it glides over and adheres to 
the surface of the amalgam. The plate is then covered 
with flannel, weights are placed upen the glass, and the 
stone is gently inclined so as to allow the excess of mer- 
cury to drain off; at the end of twenty-four hours it is 
placed upon a wooden table, the inclination of which is 
increased from day to day until the mirror assumes a ver- 
tical position : in about a month it is sufficiently drained 
to allow the mirror to be framed." — Miller. 

5 



66 THE METALS. 

88. SIL VER. — Silver was known to the ancients. 
It is found in the native state, as well as combined with 
sulphur, antimony, chlorine, and bromine. It is also 
contained in small quantities in galena, and it can be 
extracted with profit from the lead prepared from this 
ore, even when the lead contains only two or three 
ounces of silver to the ton. The method thus adopted for 
the extraction of the silver depends upon the fact that 
the whole of the silver can be concentrated into a small 
portion of lead by crystallization ; metallic lead free from 
silver separates out in crystals, and a rich alloy is left. 
When this reaches the concentration of 300 oz. of silver 
to the ton, the alloy undergoes the operation of cupella- 
tioji, in which the mixture is melted in a furnace on a 
porous bed of bone-earth, and a blast of air blown over 
the surface. The lead oxidizes, and the oxide (litharge) 
fuses, and partly runs away and partly sinks into the 
porous bed of the furnace, while the silver remains behind 
in the metallic state. 

For the extraction of silver from the other ores, a 
process termed amalga77iation is employed, in which 
mercury is used to dissolve the metallic silver. The 
argentiferous ores of Germany, in which the silver occurs 
in combination with sulphur, are roasted in a furnace 
with common salt, by which means the sulphide is con- 
verted into chloride ; the mixture is then placed in casks 
made to revolve, and scrap-iron and water are added. 
The iron reduces the silver to the metallic state, and 
when this is fully accomplished, metallic mercury is 
added ; this forms a liquid amalgam with the silver (and 
gold, if any be present), and, by distilling the mercury 
off, the silver is obtained in an impure state. Silver has 
a bright white color and a brilliant lustre, which it does 
not lose in pure air at any temperature. When melted 
in the air, it possesses the singular power of absorbing 



THE METALS. 



6 7 



mechanically a large volume (twenty-two times its bulk) 
of oxygen ; this gas it again gives out on solidifying. 

Silver is probably the best conductor of heat and elec- 
tricity known, and is extremely ductile. Sulphur com- 
bines at once with silver, forming a black sulphide ; silver 
articles long exposed to the air tarnish from this cause. 
It is because they contain a small quantity of sulphur that 
eggs, mustard, and horseradish blacken silver spoons. 
Where coal-gas is used, silver articles not unfrequently 
tarnish, owing to the fact that the sulphuretted hydrogen 
has not been thoroughly removed in the purification of 
the gas. 

89. GOLD. — Gold is usually found in the metallic 
state. It occurs in veins in the older rocks, and in the 
sands of most rivers, and, although generally found in 
small quantities, it is a widely diffused metal. In order 
to obtain the gold, the detritus or sand which contains 
the metal is washed in a cradle or other arrangement, by 
means of which the lighter particles of mud or mineral 
are washed away, while the heavier grains of gold sink to 
the bottom of the vessel. When gold has to be worked 
in the solid rock, the mineral is crushed to powder and 
then shaken up with mercury, and the gold thus extracted 
by amalgamation. 

Gold has a brilliant yellow color, and, in thin films, 
transmits green light ; it is nearly as soft as lead ; it can 
be drawn out into fine wire, and is the most malleable 
of all the metals. It does not tarnish at any tempera- 
ture, in dry or moist air ; nor is it, like silver, affected by 
sulphur. It is not acted upon by any single acid (except 
selenic), but dissolves in presence of free chlorine and 
in nitro-muriatic acid. At high temperatures, gold is 
slightly volatile. The gold used for coin is an alloy of 
gold and copper, in the proportion of 1 1 parts of gold to 



68 THE METALS. 

i of copper. This alloy is harder and more fusible, but 
less ductile, than pure gold. The purity of gold is com' 
monly expressed in carats. Pure gold is said to be 24 
carats fine; an alloy containing §f of pure gold is called 
23 carats fine; £§ of pure gold (the finest usually em- 
ployed for jewelry), 18 carats fine; and so on. 

90. PL A TINUM. — Platinum is a comparatively 
rare metal, which always occurs in the native state, and 
generally alloyed with five other metals ; namely, pal- 
ladium, rhodium, iridiwn, osmium, and ruthenium. 
This alloy occurs in small grains in detritus and gravel 
in Siberia and Brazil. 

The original mode of obtaining the metal was to dis- 
solve the ore in aqua-regia (nitro-muriatic acid), and 
precipitate the platinum (together with several of the ac- 
companying metals) with sal-ammoniac, as the insoluble 
double chloride of ammonium and platinum, 2NH 4 
Cl,PtCl 4 . This precipitate, when heated, yields metallic 
platinum in a finely divided or spongy state ; and this 
sponge, if forcibly pressed and hammered when hot, 
gradually becomes a coherent metallic mass, the particles 
of platinum welding together, when hot, like iron. A 
new mode of preparing the metal has recently been pro- 
posed, the ore being melted in a very powerful furnace, 
heated with the oxy-hydrogen blow-pipe. In this way a 
pure alloy of platinum, iridium, and rhodium is formed, 
the other constituents and impurities of the ore being 
either volatilized by the intense heat, or absorbed by the 
lime of which the crucible is composed. This alloy is in 
many respects more useful than pure platinum, being 
harder and less easily attacked by acids. 

Platinum has a bright white color, and does not tarnish 
under any circumstances in the air. It is extremely infu- 
sible, and can only be melted by the heat of the oxy- 



THE METALS. 69 

hydrogen blowpipe. It dissolves in aqua-regia, but is 
not acted upon by the ordinary acids, and hence platinum 
vessels are much used in the laboratory. Caustic alkalies, 
however, act upon the metal at high temperatures. When 
finely divided, metallic platinum has the power of con- 
densing gases upon its surface in a remarkable degree. 
When a mixture of oxygen and hydrogen is brought in 
contact with spongy platinum, the heat developed by the 
condensation of the gases is sufficient to ignite them. 

91. SALTS OF MERCURY. — Mercury forms 
two oxides, the mercurous, Hg 2 0, and the mercuric, 
HgO, and two corresponding classes of salts. The mer- 
curic sulphide, HgS, is known as cinnabar, or vermil- 
ion, much used as a paint. Mercurous chloride, Hg 2 Cl 2 , 
or calomel, and mercuric chloride, HgCl 2 , or corrosive 
sublimate, are used in medicine. The bromides and 
iodides of mercury are used in photography. 

92. SALTS OF SILVER. — Silver forms two 
oxides, Ag 4 0, argentic suboxide, and Ag 0, argentic 
oxide. The latter is the base of the ordinary silver salts. 
Argentic nitrate, AgNO s , is the most important soluble 
salt of silver. It is obtained in the form of large trans- 
parent tabular crystals, on evaporating a solution of 
silver in nitric acid. It fuses easily on heating ; and when 
cast into sticks, goes by the name of lunar caustic. This 
salt undergoes decomposition when exposed to the sun- 
light in contact with organic matter, and a black sub- 
stance, probably the suboxide, is formed ; hence it is 
employed in the manufacture of indelible ink for mark- 
ing linen and other fabrics. 

Of the insoluble silver salts, the chloride, AgCl, is the 
most important. This salt occurs in nature, and is then 
known as horn silver. It is precipitated as a white 



*]0 THE METALS. 

curdy mass, when a solution of a chloride and a silver 
salt are brought together. When exposed to the light, 
the white chloride becomes tinted of a purple color, 
which increases in shade as the action of light continues. 
This coloration arises from a partial decomposition of the 
salt, a small quantity of subchloride and free muriatic 
acid being formed. In presence of organic matter this 
change takes place much more rapidly, and upon this 
fact the art of photography depends. Argentic chloride 
is easily soluble in a solution of sodic hyposulphite, and 
it is for this reason that the latter salt is used for fixing 
photographic pictures, that is, dissolving out the unaltered 
silver salt, and thus rendering the image permanent. 
Aigeittic bronzide, AgBr, is also acted upon by the light, 
and is soluble in ammonia and an alkaline hyposulphite. 
The iodide, Agl, is a yellow powder, insoluble in water 
and ammonia, but dissolved by an alkaline hyposulphite. 
The cyanide, AgCN, as well as other salts of silver, is 
used in electro-plating. 

93. SALTS OF GOLD. — Gold forms two oxides, 
the aurous, Au 2 0, and the auric, Au 2 O s . Neither of 
these oxides forms salts -with acids, but the latter unites 
with bases to form salts called aurates. A?iric chloride, 
AuClg, obtained by dissolving gold in aqua-regia, and 
auric cyanide, Au(CN) 3 , are the most important salts of 
gold, being used in electro-gilding and photography. 

94. SALTS OF PLATLNUM. — YldXxmxm forms 
two oxides, the platinous, PtO, and the platinic, Pt0 2 . 
Platinic chloride, PtCl 4 , is the most important platinum 
compound. It is obtained as a yellowish-red solution, 
by dissolving the metal in aqua-regia. It is used in 
electro-platinizing. 



THE METALS. 7 1 

LESS USEFUL METALS. 

The less useful metals are sodium, magnesium, alu- 
minium, antimony, bismuth, and nickel. These are little 
used in a metallic state, though their compounds are of 
the highest importance. 

95. SODIUM. — This metal was discovered by Sir 
H. Davy, by the decomposition of soda with the galvanic 
current. It can be procured by reducing the carbonate 
in presence of carbon, and is now manufactured in con- 
siderable quantities for the preparation of other metals, 
especially magnesium and aluminium. Sodium is a 
silver-white metal, soft at ordinary temperatures, and 
melting at 207 ; it volatilizes below a red heat, yielding 
a colorless vapor. The compounds of sodium are very 
widely diffused, being contained in every speck of dust. 
They exist in enormous quantities in the older rocks ; but 
they are most readily obtained from sea-water, which 
contains nearly 3 per cent of sodic chloride (common 
salt), or from the large deposits of this substance which 
occur in the form of rock-salt. 

96. MA GNE SIUM. — This metal occurs in large 
quantities in combination with lime and carbonic acid, in 
dolomite or mountain limestone, and also in sea-water 
and certain mineral springs, as chloride and sulphate. 
The metal itself has only recently been prepared in 
quantity. It is best obtained by heating magnesic chlo- 
ride with metallic sodium, sodic chloride and metallic 
magnesium being formed. This metal is of a silver- 
white color, and fuses at a low red heat. It is volatile, 
and may be easily distilled at a bright red heat. When 
soft, it can be pressed into wire, and with care it may be 



72 THE METALS. 

cast like brass ; although, when strongly heated in the 
air, it takes fire, and burns with a dazzling white light, 
with the formation of its only oxide, magnesia, MgO. 
The light emitted by burning magnesium wire is distin- 
guished for its richness in chemically active rays, and is 
therefore employed as a substitute for sunlight in photog- 
raphy. It is coming to be used for purposes of illu- 
mination. 

97. ALUMINIUM. — This metal occurs in large 
quantities, combined with silicon and oxygen, in felspar 
and all the older rocks, and also in clay, marl, slate, and 
in many crystalline minerals. Metallic aluminium is 
obtained by passing the vapor of aluminic chloride over 
metallic sodium. It has recently been manufactured on 
a large scale, both in England and France, and from its 
lightness (specific gravity 2.6), its tenacity, and its bright 
lustre, it has been used for optical purposes as well as for 
ornamental work. Some of its alloys, as aluminium 
bronze, promise to become of great value in the arts. 

98. ANTIMONY. — Metallic antimony occurs native, 
but its chief ore is the trisulpkide, Sb 2 S 3 . The metal is 
easily reduced, by heating the sulphide with about half 
its weight of metallic iron, when ferrous sulphide and 
metallic antimony are formed. Antimony may also be 
reduced by mixing the ore with coal, and heating in a 
reverberatory furnace. Antimony is a bright bluish- 
white metal. It is very brittle, and can readily be pow- 
dered in a mortar. It melts at about a red heat, and may 
be distilled at a white heat, in an atmosphere of hydrogen. 
Antimony undergoes no alteration in the air at ordinary 
temperatures, but rapidly oxidizes if exposed to air when 
melted ; and if heated more strongly, it takes fire, and 
burns with a white flame, giving off dense white fumes of 



THE METALS. 73 

oxide. Antimony is not attacked either by dilute muriatic 
or sulphuric acid ; but nitric and nitro-muriatic acid dis- 
solve it easily. The alloys of antimony are largely used 
in the arts. Of these, type-metal (an alloy of lead and 
antimony) is the most important; it contains from 17 
to 20 per cent of the latter metal. 

99. BISMUTH. — This metal is found in small quan- 
tities in the native state, but occurs more often as a sul- 
phide ; it is easily reduced to the metallic state, and then 
exhibits a pinkish-white color. It melts at S°7°i an d is 
volatilized at a white heat. Bismuth does not oxidize in 
dry air at the ordinary temperature ; but if heated strongly, 
it burns with a blue flame, forming an oxide ; it also takes 
fire when thrown into chlorine gas. Bismuth dissolves 
easily in nitric acid. The metal is chiefly used as an in- 
gredient of fusible metal. The alloy of 2 parts of bis- 
muth, 1 of lead, and 1 of tin, melts at 201 c ; that of 
8 parts of bismuth, 5 of lead, and 3 of tin, melts at 21 2°. 
The compounds of bismuth are used in the porcelain 
manufacture, in medicine, and as cosmetics. 

Both bismuth and antimony closely resemble arsenic 
in the compounds which they form. Thus we have 
Sb 2 O s , Sb 2 O s , and H 3 Sb ; Bi 2 O s and Bi 2 O s (6>j). Hence 
bismuth and antimony are now generally classed among 
the non-metallic elements of the nitrogen group. 

100. NICKEL. — Nickel occurs in large quantities 
combined with arsenic, as kupfernickel ; also together 
with cobalt in speiss ; and it is now prepared in consider- 
able quantities for the manufacture of German silver, an 
alloy of nickel, zinc, and copper. Nickel is a white, 
malleable, and tenacious metal ; it melts at a somewhat 
lower temperature than iron, and is strongly magnetic, 
but loses this property when heated to above 6oo°. 



^4 THE METALS. 

ioi. SALTS OF SODIUM. — There are two com- 
pounds of sodium and oxygen, Na 2 0, sodic oxide, and 
Na 2 2 , sodic peroxide. Sodic oxide has a strong affinity 
for water, with which it combines to form NaHO, sodic 
hydrate {caustic soda). This is a white solid, very 
soluble in water, very caustic and alkaline, and is largely 
used in making soap. 

Caustic soda is now manufactured on a very large 
scale, by boiling lime and sodic carbonate (carbonate of 
soda) with water, and evaporating down the clear solu- 
tion. The reaction is as follows : — 

CaO + Na 2 CO s + H 2 = CaCO s + zNaHO. 

1 02. Sodic CJiloride. — Sodic chloride, NaCl, is com- 
mon salt. It is from this compound that nearly all the 
other sodic compounds are prepared. 

In Southern Europe, on the shores of the Mediter- 
ranean, large quantities of salt are obtained from sea- 
water. The water is allowed to flow into large shallow 
pools, called salt-pans ■, where it is evaporated by the 
agency of the air and the sun. Only pure water passes 
off in the form of vapor, and the solution grows more 
and more concentrated. After a time, the brine is 
pumped into large iron pans, and evaporated by arti- 
ficial heat until the salt crystallizes. 

In many parts of the earth there are salt lakes, often 
called seas. The streams flowing into them are more or 
less impregnated with salt, which they dissolve from the 
soil over which they flow. Such lakes are natural salt- 
pans, for the water which is evaporated from them is 
pure, and they consequently become more and more 
saturated with salt, till it is finally deposited on the 
bottom in solid crystals. The most remarkable of these 
lakes is the Great Salt Lake in Utah. 

Such salt lakes appear to have existed in all geological 



THE METALS. fa. 

ages, and by long-continued evaporation to have given 
rise to large masses of solid salt, called rock salt. These 
beds of rock salt are found in all parts of the earth. The 
most remarkable are at Wieliczka in Poland, and at Car- 
dona in Spain. The former is 500 miles long, 20 miles 
broad, and 1,200 feet deep. It has been worked for 
several centuries. Some of the galleries excavated in it 
are 30 miles long. The bed at Cardona is a " mountain 
of salt," 400 or 500 feet high, and the salt is of the 
greatest purity. 

Salt is obtained from these beds sometimes by exca- 
vation and sometimes by solution. In the latter case, a 
hole is sometimes bored down to the bed of salt, often to 
the depth of 1 ,200 or 1 .500 feet. A tube somewhat smaller 
than the bore is then introduced, and fresh water allowed 
to flow down outside the tube. This water, on reaching 
the bed, becomes saturated with salt, and rises in the 
tube. Since, however, it is heavier than fresh water, it 
will not rise to a level with the latter on the outside of 
the tube. If the bore is 1,200 feet deep, the brine will 
rise within about 200 feet of the top. It must be pumped 
up the remaining distance. The solution is then evapo- 
rated, and solid salt obtained. 

It not unfrequently happens that natural springs occur 
in such localities that their waters come into contact with 
beds of* salt. Such springs are called salt springs, or 
brine springs. They sometimes come to the surface ; 
but oftener they can only be reached by boring, and the 
brine brought to the surface by means of the pump. The 
water of these natural springs is usually less concentrated 
than that of the artificial springs described above. In 
England and in this - country the salt produced is nearly 
all obtained from brine springs. 

The most important salt springs of this country are in 
Central New York, in Virginia, and in Pennsylvania. 



j6 . THE METALS. 

About 6,000,000 bushels of salt are produced annually 
in New York. When the brine is not a saturated solu- 
tion, it is usually concentrated by partially evaporating it 
in large shallow pans by the air and the sun. It is then 
further concentrated and crystallized by artificial heat. 

103. Sodic Carboiiate. — Sodic carbonate, Na 2 C0 3 , 
is known in commerce as soda-ash, and is manufactured 
on an enormous scale. It is largely used in glass-mak- 
ing, soap-making, bleaching, and many other processes 
in the arts. 

Before the French Revolution, the Continental nations 
of Europe derived their soda-ash mainly from Spain, 
where it was made from the ashes of certain marine 
plants, which contain a large amount of soda. The soda- 
ash thus obtained was called barilla. 

In England, the soda-ash used "was mainly obtained 
from the ashes of a sea-weed called kelp, which grows 
abundantly on the north and west coast of Ireland, and 
on the west coast and the islands of Scotland. 

One of the first effects of the war of the French Rev- 
olution was to cut off the supply of alkali from Spain. 
About this time, a French chemist, Le Blanc, discovered 
a process by which sodic carbonate, or soda-ash, could 
be obtained from common salt, or sodic chloride, NaCl. 
This process became publicly known through a commis- 
sion appointed, during the first year of the Republic, to 
investigate the subject of alkali manufacture. 

Le Blanc's method is the same as that now used in the 
making of sodic carbonate, which has come to be one of 
the most important branches of chemical manufacture. 
The process may be divided into two stages : — 

(1) Manufacture of sodic sulphate, or salt-cake, from 
sodic chloride ; called the salt-cake process. 

(2) Manufacture of sodic carbonate, or soda-ash, from 
salt-cake ; called the soda-ash process. 



THE METALS. 



77 



(i) Salt-cake Process. — This consists in the decom- 
position of salt, by means of sulphuric acid. This is 
effected in a furnace, called the salt-cake furnace, a sec- 
tion of which is represented in Figure 17. It consists 

Fig. 17. 

ml 




of a large covered iron pan, placed in the centre of the 
furnace, and heated by a fire placed underneath ; and two 
roasters, or reverberatory furnaces, placed one at each 
side, on the hearths of which the salt is completely de- 
composed. The charge of half a ton of salt is first placed 
in the iron pan, and the sulphuric acid allowed to run in 
upon it. Hydric chloride (muriatic acid) is evolved, 
and escapes through a flue with the products of combus- 
tion into towers, or scrubbers, filled with coke or bricks 
moistened with a stream of water ; the acid vapors are 
thus condensed, while the smoke and heated air pass up 
the chimney. The reaction is as follows : — 

2NaCl -f H 2 S0 4 == Na 2 S0 4 + 2HCI. 

After the mixture of salt and acid has been heated for 
some time in the iron pan, and has become solid, it is 
raked out upon the hearths of the roasters, where the 
flame and heated air of the fire complete the decomposi- 
tion into sodic sulphate and hydric chloride. 

(2) Soda-ash Process. — This consists (1) in the 
preparation of the sodic carbonate, and (2) in the sepa- 
ration and purification of the same. The first chemical 
change which the salt-cake undergoes is its reduction to 
sodic sulphide, by heating it with powdered coal : — 

Na 2 S0 4 + C 4 = Na 2 S + 4CO. 



^8 THE METALS. 

The second decomposition is the conversion of the sodk 
sulphide into sodic carbonate, by heating it with chalk or 
limestone (calcic carbonate) : — 

Na 2 S + CaC0 3 =Na 2 C0 3 + CaS. 

These two reactions are, in practice, carried on at 
once ; a mixture of 10 parts of salt-cake, 10 parts of 
chalk or limestone, and >].$ parts of coal, being heated in 
a reverberator}' furnace, called the balling furnace, until 
it fuses, and the decomposition is complete, when it is 
raked out into iron wheelbarrows to cool. This process 
is generally called the black-ash process, from the color 
of the fused mass. 

The next operation consists in the separation of the 
sodic carbonate from the insoluble calcic sulphide and 
other impurities. This is easily accomplished by lixivi- 
ation, or dissolving the former salt out in water. On 
evaporating down the solution, for which the waste heat 
of the balling furnace is used, and calcining the residue, 
the soda-ash of commerce is obtained. 

No less than 200,000 tons of common salt are annually 
consumed in the alkali works of Great Britain, for the 
preparation of nearly the same weight of soda-ash, the 
value of which is about $10,000,000. 

104. Bicarbonate of Soda. — The salt known as bi- 
carbonate of soda, HNaC0 3 , is obtained by exposing the 
crystallized sodic carbonate in an atmosphere of carbonic 
acid. It is a white crystalline powder, used in medicine 
and for making effervescing drinks ; also in bread-mak- 
ing, as a substitute for yeast. 

105. Other Sodic Salts. — Sodic nitrate {soda salt- 
petre), NaN0 3 , is found in northern Chili in large beds. 
It is used in making nitric acid, and as a manure. 

Sodic sulphate {sulphate of soda), Na 2 S0 4 , is famil- 
iarly known as Glauber's salts. 






THE METALS. 79 

Sodic hyposulphite {hyposulphite of soda) is used in 
photography (92). 

Sodic borate, or borax, is considerably used in the ails, 
especially as a Jlux in soldering. It dissolves the oxide 
formed upon the surfaces to be united, and thus keeps 
them clean and bright. 

Sodic silicate {silicate of soda) is called soluble glass, 
and is used to some extent as a paint or varnish for fixing 
fresco colors, and for preserving stone-work, and quite 
largely in calico printing and dyeing. 

106. SALTS OF MA GJVFSIUM. — Magnesium 
has but one oxide, MgO, or magnesia. The most im- 
portant salt of this oxide is the magnesic sulphate or 
Epsom salts, used in medicine. 

107. SALTS OF ALUMINIUM. — Tte only ox- 
ide of aluminium is alumina, Al 2 O g . It occurs native in 
a nearly pure and crystalline state as corundum, ruby, 
sapphire, and emery. Alumina is largely used as a mor- 
dant in dyeing and calico-printing, as it has the power of 
forming insoluble compounds, called lakes, with vegeta- 
ble coloring-matter, and thus fixes the color in the pores 
of the cloth so that it cannot be washed out {86). 

The soluble aluminic sulphate, A1 2 3S0 4 , is prepared on 
a large scale for the use of the dyer, by decomposing clay 
by the action of sulphuric acid. The solid mixture of 
silica and aluminic sulphate thus obtained goes by the 
name of alum-cake. The most useful compounds of 
alumina are, however, the alums, a ssrics of double salts, 
which aluminic sulphate forms with the alkaline sul- 
phates. Common • potash alum has the composition 
K 2 A1 2 4 S0 4 . It may be prepared by dissolving the two 
sulphates together, and allowing the compound salt to 
crystallize, .but it is usually obtained from the decompose- 



bO THE METALS. 

tion of a shale or clay containing iron pyrites, FeS 2 . 
This substance gradually undergoes oxidation when the 
shale is roasted (taking oxygen from the air), producing 
sulphuric acid, which unites with the alumina of the clay, 
and, on the addition of a potassic compound, alum crys- 
tallizes out. A salt called ammonium alum, and con- 
taining H 4 N, instead of K, is at present prepared on a 
large scale ; the ammonia liquor of the gas-works, to- 
gether with sulphuric acid, being added to the burnt 
shale, instead of a potash salt. 

There are several other alums known, in which iron, 
chromium, or manganese takes the place of the alumin- 
ium in common or potash alum. 

Clay is an aluminic silicate resulting from the disin- 
tegration and decomposition of felspar by the action of 
air and water. Kaolin or porcelain clay is the purest 
form of clay, containing no iron or other impurities. 
There are many very beautifully crystalline minerals, as 
garnet and mica, consisting of aluminic silicates com- 
bined with silicates of other metals. 

108. Glass, Porcelain, a7id Earthen-ware. — The 
silicates of the alkalies are soluble in water and non- 
crystalline ; those of the alkaline earths (Ba, Sr, and Ca), 
are soluble in acid and crystalline ; while compounds of 
the two are insoluble in water and acids, and do not as- 
sume a crystalline form. Such a compound, when fused, 
is termed a glass. There are four different kinds of glass 
used in the arts, differing in their chemical composition, 
and exhibiting corresponding differences in their proper- 
tics : (i) Crown or 'window and plate glass, composed 
of silicates of soda and lime ; (2) Bohemian glass, con- 
sisting of silicates of potash and lime ; (3) Jlint glass or 
crystal, containing silicates of potash and lead ; and (4) 
common green bottle-glass, composed of silicates of soda, 
lime, iron, and alumina. The first and third of these 



THE MZTALS. 8 1 

kinds of glass are easily fusible, while the second or pot- 
ash glass is much less fusible ; the addition of plumbic 
oxide increases the specific gravity and lustre of the glass 
as well as its fusibility. The common glass articles of 
household use are generally made of flint glass, while for 
chemical apparatus a soda-lime glass is to be preferred. 
The potash-lime glass is much employed where an infu- 
sible or hard glass is needed. The fourth kind of glass 
is an impure mixture of various silicates, employed for 
purposes in which the colors and fineness of the glass are 
not of consequence. 

In the preparation of all the fine qualities of glass, 
great care is requisite in the selection of pure materials, 
as well as in the processes of manufacture. Generally 
the materials are melted together with a quarter to 
a half their weight of cullet, or broken glass of the 
same kind. After the glass articles have been blown 
or cast, they must be annealed, that is, made less brit- 
tle by being very slowly heated and as slowly cooled in 
an oven arranged for the purpose. 

Certain metallic oxides have the power of coloring 
glass when they are added in small quantity. Thus fer- 
rous oxide produces a deep green color (bottle-glass), 
while the oxides of manganese impart a purple tint to 
glass. Advantage is taken of this in the preparation of 
colorless glass, for as it is difficult to obtain materials 
perfectly free from iron, which imparts -a green color, a 
small quantity of black oxide of manganese is added to 
the mixture, and the violet color thus produced neu- 
tralizes the green, and a nearly colorless glass is the result. 
The addition of arsenious oxide effects the same end by 
oxidizing the ferrous to ferric oxide. The colors of pre- 
cious stones are imitated by adding certain oxides to a 
brilliant lead glass called paste ; thus the blue of the sap- 
phire is given by a small quantity of cobaltic oxide, 

6 



S2 THE METALS. 

while cuprous oxide imparts a ruby-red color, and ferric 
^>xide a yellow color resembling topaz. 

The various forms of forcelaht and earthen-ware 
consist of aluminic silicate or clay in a more or less pure 
state, covered with some substance which fuses at a 
high temperature, and forms a glaze, giving a smooth 
surface and binding the material closely together, and 
^hus filling up the pores of the baked clay. For the 
manufacture of porcelain the finest kaolin or China clay 
is used, while for common earthen-ware an inferior clay 
may be employed. The glaze used for porcelain is gen- 
erally finely powdered felspar, the biscuii\ or porous 
ware, being first dipped into a vessel containing this sub- 
stance suspended in water and then strongly heated. 
The articles thus coated can be used for chemical pur- 
poses, as this glaze withstands the action of acids. For 
earthen-ware the so-called salt glaze is used ; obtained 
by throwing some common salt into the furnaces contain- 
ing the strongly heated ware. The salt is volatilized and 
undergoes decomposition on the heated surface, deposit- 
ing a fusible silicate upon it, and rendering the ware 
impervious to moisture. 

109. SALTS OF ANTIMONY. — Antimony has 
two oxides, Sb 2 O s , and Sb 2 O s , and two corresponding 
sulphides and chlorides. The most important of its salts 
is tartar-emetic, or tartrate of antimony and fiotask, 
used in medicine. 

no. SALTS OF BISMUTH. -* Bismuth forms 
two oxides, analogous to those of antimony. The most 
important of the salts is the nitrate, Bi3N0 3 , which is 
easily procured by dissolving the metal in nitric acid. 

in. SALTS OF NICKEL. — There are two 



THE METALS. 



»3 



oxides of nickel, NiO, and Ni 2 O s . The former of these 
gives rise to salts which have a peculiar apple-green 
color. The latter is a black powder, prepared by adding 
a solution of bleaching-powder to a soluble nickel salt. 
The most important soluble salt is the nitrate, Ni2N0 3 . 

METALS NOT USED IN A FREE STATE, BUT 
VALUABLE FOR THEIR SALTS. 

There are certain metals which are not used in a free 
state, but which form salts of considerable importance. 
These metals are -potassium, calcium, strontium, barium, 
ma7iganese, chromium, and cobalt. 

112. POTASSIUM. — This metal was discovered 
in the year 1807, by Sir Humphrey Davy, who decom- 
posed potash by means of a powerful galvanic current. 
Before this time the alkalies and alkaline earths were 
supposed to be elementary bodies. The metal is now 
prepared by heating together potash and carbon to a high 
temperature in an iron retort. 

Potassium is a bright, silver-white metal, which can be 
easily cut with a knife at the ordinary temperature ; it is 
brittle at 32 , and melts at 144 . It rapidly absorbs 
oxygen when exposed to the air, and becomes converted 
into a white oxide. 

The original source of potassic compounds is in the 
felspar of the granitic rocks, as these contain from .02 to 
.03 of this metal. Up to the present time, no cheap and 
easy mode has been found of separating the potash from 
the silicic acid with which it is combined in felspar. 
Plants, however, are able slowly to separate out and 
assimilate the potash from these rocks and soils ; so that, 
by burning the plant and leaching the ashes with water, 
soluble potash-salt is obtained. 



6^ THE METALS. 

This is the crude potassic carbonate, called, when 
purified by crystallization, pear lash. It is the substance 
from which most of the potassic compounds are obtained. 

The most important compounds of potassium are 
caustic potash, KHO, potassic carbojiate (carbonate oj 
potash), K 2 CO s , and potassic nitrate, or saltpetre, 
KN0 3 . This last compound readily parts with its oxy- 
gen, and is therefore extensively used in making gun- 
powder and fireworks. • 

Gunpowder consists of an intimate mixture of salt- 
petre, charcoal, and sulphur. When the gunpowder is 
ignited, the sulphur and charcoal burn at the expense of 
the oxygen in the saltpetre, while the nitrogen is set free. 
It is to the expansive force of the large volume of gases 
suddenly set free in a confined space, that the destructive 
power of gunpowder is due. 

Potassic chlorate, KC10 3 , gives up its oxygen even 
more readily than the nitrate, and is used, as we have 
seen, in the preparation of oxygen (10). It is also used 
in making fireworks and percussion caps. 

113. CALCIUM. — Calcium forms a considerable 
portion of the rocks of wnich the earth is composed, and 
occurs in very large quantities, forming whole mountain 
chains of chalk, gypsuni, and limestone. The metal is 
obtained by the decomposition of the chloride by the elec- 
tric current, or by heating the iodide with sodium. It is 
a light, yellow metal, which easily oxidizes in the air. 
When heated in air, it burns with a bright light, forming 
lime, CaO, the only oxide of calcium. 

Lime is prepared on a large scale for building and 
other purposes, by heating limestone (the carbonate) in 
kilns by means of coal mixed with the stone ; the car- 
bonic acid escapes, and quicklime or caustic lime re- 
mains. Pure lime is a white, infusible substance, which 



THE METALS. 85 

combines with water very readily, giving off great heat, 
and falling to a white powder called calcic hydrate, or 
slaked lime. The hydrate is slightly soluble in water, 
1 part of it dissolving in 730 parts of cold, but only in 
1,300 parts of boiling water, and forming lime-water, 
which, like the hydrate, has a great power of absorbing 
carbonic acid from the air. It is indeed partly owing to 
this property that the hardening or setting of mortars 
and cements made from lime is due. Mortar consists of 
a mixture of slaked lime and sand. A gradual combi- 
nation of the lime with the silica occurs, and this helps 
to harden the mixture. Hydraulic cemcjit, which 
hardens under water, is prepared by carefully heating an 
impure lime containing clay and silica ; a compound 
silicate of lime and alumina appears to be formed on 
moistening the powder, which then solidifies, and is not 
acted upon by water. Lime is largely used in agricul- 
ture, its action being, (1) to destroy the excess of 
vegetable matter contained in the soil; and (2) to lib- 
erate the potash for the use of the plants from heavy 
clay soils by decomposing the silicate. 

Calcic carbonate (cai'bonate of lime) CaC0 3 occurs 
most widely diffused, as chalk, limestone, coral, and 
marble ; many of those enormous deposits being made 
up of the microscopic remains of minute sea-animals. 
The carbonate is almost insoluble in pure water ; but 
readily dissolves when the water contains carbonic acid, 
and is deposited again, in crystals, as the gas escapes. 
In this way enormous masses of crystalline limestone are 
formed. Water charged with carbonic acid and calcic 
carbonate makes its way through the roof of limestone 
caverns, and, as the carbonic acid gradually escapes, the 
calcic carbonate is deposited in dependent masses, like 
icicles, termed stalactites ; while the water, falling on 
the floor of the cavern before it has parted with all its 



86" THE METALS. 

carbonic acid and dissolved limestone, deposits a fresh 
portion of the crystalline matter, and thus a new growth, 
or stalagmite, gradually rises to meet the stalactite 
which hangs from the roof. In this way a natural pillar 
of limestone is formed. 

Calcic sulphate, CaS0 4 , occurs in nature, combined 
with 2H 2 0, as gypsum or alabaster. It is soluble in 
400 parts of water, and is a very common impurity in 
spring water, giving rise to a hardness which cannot be 
removed by boiling. Gypsum, when moderately heated, 
loses its water, and is then called plaster of Paris ; this, 
when moistened, takes up two atoms of water again and 
sets to a solid mass, and is therefore much used for 
making casts and moulds. 

Calcic chloride {chloride of calciunz), CaCl 2 , is 
formed when limestone or marble is dissolved in muri- 
atic acid ; if the solution be then evaporated, colorless 
needle-shaped crystals are obtained. When these are 
dried, they form a porous mass which takes up moisture 
with great avidity, and is much used for drying gases. 

1 14. STR ONTIUM. — This element occurs in much 
smaller quantities than calcium, being found jn only a 
few minerals. It likewise occurs in minute quantities in 
certain spring waters. The metal has a yellowish-white 
color, and is prepared by the action of a current of elec- 
tricity on the fused chloride. It resembles calcium 
closely in its properties. When heated in the air, it- 
burns, forming the oxide strontia. 

The native salts of strontium, the carbonate and sul- 
phate, are insoluble, and serve for the preparation of the 
remaining salts. The nitrate, Sr2N0 3 , and the chloride, 
SrCl 2 , are soluble in water. These are the only salts of 
this metal which are employed in the arts. They are 
used for the preparation of red Jires, as the volatile 






THE METALS. 87 

salts of strontium have the power of coloring the flame 
crimson. 

115. BARIUM. — Barium compounds occur some- 
what more widely dispersed than those of strontium, the 
two most common barium minerals being the sulphate. 
or heavy spar, and the carbonate, or witherite. The 
metal barium has not yet been obtained in the coherent 
state ; but the metallic powder may be prepared in the 
same way as calcium and strontium, which it closely re- 
sembles in its properties. 

The most important barium compounds are the chlo- 
ride and the nitrate, used as tests for sulphuric acid, and 
for giving a green color to the flame in fireworks. 

116. CHROMIUM. — Chromium is a substance 
whose compounds do not occur very widely distributed, 
or in large quantities. They are, nevertheless, much 
used in the arts as pigments, many of them having a fine 
bright color. The chief ore of this metal is a compound 
of the oxides of chromium and iron, called chrome iron- 
stone, found in America, Sweden, and the Shetlands. 
A compound of chromium, lead, and oxygen, called 
plumbic chromate {chromate of lead), is also found. 
Pure chromium appears to be the most infusible of all 
the metals, as it cannot be melted at a temperature 
sufficient to fuse and volatilize platinum. 

Chromium forms three oxides : chromous oxide, CrO, 
chromic oxide, Cr 2 3 , and chromic peroxide, Cr0 3 - 
which, dissolved in water, has a strong acid reaction, 
and may then be called chromic acid. It neutralizes 
bases, and forms yellow or red salts, called chromates. 
The most common of these are known as the chromate 
and bichromate of potash, K 2 Cr0 4 and K 2 Cr 2 O r The 
former is a yellow salt, and the latter a red salt, which 



88 THE METALS. 

is made on a large scale, and used in the preparation of 
the various chrome pigments. 

The chief of the insoluble chromates is plumbic 
chromate, PbCr0 4 , or chrome yellow, obtained by pre- 
cipitating a potassic chromate by a soluble lead salt, 
and largely used for dyeing and other purposes. 

117. COBALT. — Cobalt is never found in a free 
state except in small quantities in meteoric iron. It is 
almost as infusible as iron. It is of a reddish-gray color, 
hard, and strongly magnetic. It is not used in a metallic 
state, but many of its compounds are remarkable for the 
beauty of their colors, and are used as pigments. It 
forms two oxides, CoO and Co 2 3 . The zajfre of com- 
merce is a very impure oxide of cobalt, mixed with two 
or three times its weight of sand. It is used for coloring 
glass. Thenard 's blue, or artificial ultramarine, is a 
compound of cobaltic and aluminic oxides. 

118. MANGANESE. — Manganese occurs in nature 
as an oxide, and it can be obtained, though with diffi- 
culty, in the metallic state, by heating the oxide very 
strongly with charcoal. The metal is of a reddish-white 
color ; it is brittle, and hard enough to scratch glass. It 
decomposes water at the ordinary temperature with evo- 
lution of hydrogen ; it cannot be preserved in the air 
without undergoing oxidation, and must be kept under 
naptha, or in a sealed tube ; it is slightly magnetic, and, 
like iron, combines with carbon and silicon. Metallic 
manganese is not used in the arts ; but an alloy of this 
metal and iron is now made on a large scale, and used 
in the manufacture of steel. Some of its oxides are used 
for evolving chlorine from muriatic acid, and also for 
giving glass a purple color. 

Manganese forms several well-marked oxides : (1 ) man' 






THE METALS. 89 

ganous oxide, MnO, a basic body, furnishing a series of 
salts ; (2) ma?iganic oxide, Mn 2 O s , which also forms 
salts, but of a much less stable character ; (3) black 
oxide, Mn0 2 , a neutral substance, occurring as an ore 
of manganese ; (4) and (5) two acid oxides, which give 
rise to salts known as manganates and permanganates. 

Black oxide of manganese is found in many parts of 
Europe ; but the most productive mines are in Thuringia 
and Moravia. More than 18,000 tons are used annually 
in England in the manufacture of bleaching powder. 

THE RARER METALS. 

The other metallic elements are very rare substances, 
and as yet are of very little practical importance. 

119. Cadmium (Cd) is a white metal resembling tin, 
and is found in small quantities in the ores of zinc. It 
is remarkable for forming very fusible alloys. For ex- 
ample, an alloy of 15 parts of bismuth, 8 of lead, 4 of tin, 
and 3 of cadmium, melts at about 140 F. The sulphide 
is a valuable yellow pigment, and the iodide is used to 
some extent in photography. 

120. Iridium (Ir) is the heaviest of the metals. An 
alloy of iridium and osmium is very hard, and is used 
for the points of gold pens. It forms three oxides, which 
readily pass one into another, giving rise to the variety 
of tints which characterize the solution of its salts. It is 
because of these changes of color that the metal is called 
iridium, from iris, the rainbow. 

121. Tungsten, or wolfranium (W), forms with steel 
an alloy of remarkable hardness. W0 3 , or tungstic acid, 
combines with sodium to form sodic tungstate {ttmg- 
state of soda), Na 2 W0 4 , which is used in calico-printing, 
and in combination with starch to render linen and 
cotton fabrics incombustible. 



9° 



THE METALS. 



122. Uranium (U) forms an oxide, UO, which gives 
a peculiar yellow color to glass, and also renders it 
fluorescent. 

The other metals are of too little use or interest to be 
mentioned here. 



SUMMARY. 

The metals are seldom found in a free state, but 
usually combined with other elements as ores. Their 
separation from these ores is called reduction. 

The most useful metals are iron, lead, copper, tin, 
and zinc. 

The noble metals are gold, silver, mercury, and plat- 
inum. 

The less useful metals are sodium, magnesium, alu- 
minium, antimony, bismuth, and nickel. 

The metals not used in a free state, but valuable for 
their salts, are potassium, calcium, strontium, barium, 
manganese, chromium, and cobalt. 

Among the rarer metals, cadmium, iridium, tungsten, 
and uranium are of some interest. 

Among the most important metallic compounds may 
be mentioned : salt, soda-ash, soda saltpetre, caustic soda, 
bicarbonate of soda, pearlash, saltpetre, caustic potash, 
lime, alum, glass, porcelain, green vitriol, blue vitriol, 
white vitriol, litharge, red lead, and white lead. 



CHEMISTRY OF THE ATMOSPHERE. 



COMBUSTION. 

123. Composition of the Atmosphere. — We live at 
the bottom of an aerial ocean called the atmosphere, 
which is some fifty miles in depth. This atmosphere 
contains free oxygen ; as may be shown by inverting a 
jar of it over a jar of nitric oxide. The gases, on mix- 
ing, become cherry-red (33). 

Burn a piece of phosphorus in a jar of air over water. 
The jar is filled with dense white fumes, which are soon 
absorbed by the water, which rises and partially fills the 
jar. Introduce now some nitric oxide into the jar while 
still over the water, and the gas shows no trace of red 
color. The free oxygen then can be removed from the 
air by burning phosphorus in it. After all the oxygen 
has combined with the phosphorus, and the compound 
formed has been absorbed by the water, the jar is found 
to be about one-fifth filled with water ; showing that 
about one-fifth of the air is oxygen. 

The gas remaining in the jar is found to be almost 
pure nitrogen. 

Besides the oxygen and nitrogen, there is a small 
quantity of carbonic anhydride (carbonic acid) ; as may 
be shown by passing a large volume of air through lime- 
water. There is also watery vapor, which is continu- 
ally condensed in the form of rain and dew. A trace 
of ammonia, and of nitric acid, is also found ; and to 



92 THE CHEMISTRY OF THE ATMOSPHERE. 

these are to be added the exhalations continually rising 
from the earth. The whole quantity of these minor in- 
gredients, with the exception of watery vapor, does not 
amount to more than one part in a thousand. The pro- 
portions of oxygen and nitrogen are almost invariable, 
while those of the other ingredients are continually fluc- 
tuating. 

It must be borne in mind that the atmosphere is not a 
chemical compound, but merely a mixture of these dif- 
ferent gases. " Indeed, we may regard the globe as sur- 
rounded by at least three separate atmospheres, — one of 
oxygen, one of nitrogen, and one of aqueous vapor, — all 
existing simultaneously in the same space, yet each en- 
tirely distinct from the other two, and only very slightly 
influenced by their presence." 

The following Tables are from Miller : — 

Composition of the Atmosphere* 

Oxygen 20.61 

Nitrogen 77-95 

Carbonic Acid . . ' . . .04 

Watery Vapor (average) 1 .40 

100.00 

Composition in Tons. 
Oxygen .... 1,233,010 billions of tons. 
Nitrogen .... 3,994>593 » ->•> 

Carbonic Acid . . 5,287 „ „ 

Watery Vapor . . 54460 „ „ 

124. The Products of the Burning of a Candle or 
Coal- Gas are Carbonic Acid and Water. — When a 
lighted taper is held to a candle, or to a jet of coal-gas, 
the latter takes fire. In what does its burning consist ? 



THE CHEMISTRY OF THE ATMOSPHERE. 93 

Invert a bottle for a short time over the candle or gas- 
burner ; then remove it, pour in a little lime-water, close 
the mouth of the bottle with the hand, and shake it. The 
lime-water becomes milky-white ; showing that carbonic 
acid has been produced by the burning. 

If the candle or gas be burnt under a tin funnel con- 
nected with a long glass tube (which must be kept cold), 
moisture will collect on the inside, and, after a short time, 
will trickle down, and drop from the end of the tube. 
When potassium is put into water, it burns with a rose- 
colored flame. If the liquid from the tube be tested 
with a bit of potassium, it proves to be water, which 
is therefore another product of the burning. 

Fig. 18. 



No other substance is produced, except in very minute 
quantities, by the burning of the candle or the gas. 

125. The Candle, in Burning, removes Oxygen from 
the Air. — Arrange a candle, so that it can be covered 
with a bell-jar, over the water-trough ; then light it, and 
cover it with the jar. It soon ceases to burn, and the 
water rises in the jar. The burning, then, removes some- 
thing from the air. 

Put a lighted candle into air from which the oxygen 
has been removed, and it is at once extinguished ; show- 
ing that it cannot burn without oxygen. It must then be 
oxygen which it removes from the air when it burns. 



94 THE CHEMISTRY OF THE ATMOSPHERE. 

126. All ordinary Combustion consists in the Com- 
bination of the Oxygen of the Air with the burning 
Substance. — We have seen that carbonic acid, C0 2 , 
and water, H 2 0, are the products of the burning of a 
candle. Of the three elements in these products, the O, 
as we have seen, comes from the air ; the C and H exist 
in the candle. 

The force, then, which causes the candle to burn, is 
affinity, and the burning is the combination of the oxy- 
gen of the air with the elements of the candle. 

Experiments similar to those which we have tried with 
the candle, will show that any ordinary combustible sub- 
stance removes oxygen from the air when it burns, and 
that it cannot burn without oxygen. We conclude, then, 
that all ordinary combustion is the combination of the 
oxygen of the air with the burning body. 

127. Why a Draft is necessary in Stoves and Fur- 
naces. — We see now why our stoves and furnaces must 
have a draft. As fast as the oxygen is taken from the 
air by the burning fuel, this air must be removed, and a 
fresh supply must take its place. In other words, a 
stream of air must be kept constantly flowing over or 
through the fuel. 

We see, also, how the fire can be regulated by means 
of the draft. If the doors or dampers through which 
the air is admitted be partially closed, the supply of air 
will be diminished, and the burning will therefore be 
retarded. 

128. Combustibles and Supporters of Combustion. — 
Any substance, as coal-gas, which can be made to burn, 
is called a combustible ; while any substance, as air or 
oxygen, in which it can burn, is called a supporter of 
combustion. These terms are convenient, though, strictly 
speaking, the one substance is no more a combustible or 
a supporter of combustion than the other. Since the 



THE CHEMISTRY OF THE ATMOSPHERE. 



95 



Fig. 19 



burning of coal-gas consists in the combination of the gas 
with oxygen, the oxygen in reality burns, as well as the 
gas ; and, on the other hand, the gas is as much a sup- 
porter of the combustion as the oxygen. The burning 
must of course take place where the gases come together. 
A jet of oxygen would appear to burn in an atmosphere 
of coal-gas, just as a jet of coal-gas appears to burn in an 
atmosphere of oxygen. 

Fit a cork to one 
end of a lamp chim- 
ney, and let the tip 
of a gas-burner pass 
through it, as repre- 
sented in the figure. 
Allow the gas to es- 
cape for some time, 
and then light it at the 
top of the chimney. 
It will burn quietly, 
and the chimney will 
evidently be filled 
with coal-gas. Fill a gas-bag with oxygen, and fasten 
to the bag a bent glass tube drawn out into a fine jet. 
Force the oxygen through the tube in a gentle stream, 
and introduce the end of the tube through the flame into 
the chimney. As it passes the flame, the oxygen takes 
fire, and burns brightly in the coal-gas ; the oxygen ap- 
parently becoming the combustible body, and the coal- 
gas the supporter of combustion. 

In both the flames which we have here, it will be seen 
that gases are burning where they come together ; — the 
coal-gas and the oxygen of the air, where they meet at 
the top of the chimney ; the oxygen from the bag and the 
coal-gas, where they meet at the end of the tube inside 
the chimney. 




96 THE CHEMISTRY OF THE ATMOSPHERE. 

129. Oxygen must be Heated before it will combine 
with ordinary Combtistibles. — The jet of coal-gas has 
no disposition to burn until a lighted taper is applied 
to it. The oxygen of the air is at all times in contact 
with wood and coal, yet they do not burn unless they are 
first kindled. When even as inflammable a gas as hy- 
drogen is mixed with oxygen, it does not burn unless 
ignited with a taper or an electric spark. " At the ordi- 
nary temperature of the air its chemical affinities are 
dormant ; and, although endowed with forces which are 
irresistible when in action, it awaits the necessary con- 
ditions to call them forth. One of the grandest works of 
ancient art which have come down to us, is the colossal 
statue of the Farnese Hercules. The hero of ancient 
mythology is represented in an erect form, leaning on his 
club, and ready for action ; but at the moment every one 
of the well-developed muscles of his ponderous frame is 
fully relaxed, and the figure is a perfect ideal of repose, 
yet a wonderful embodiment of power. Here in this 
antique we have most perfectly typified the passive con- 
dition of oxygen, the hero of the chemical elements. 
Raise now the temperature to a red heat, and in a mo- 
ment all is changed. The dormant energies of its mighty 
powers are aroused, and it rushes into combination with 
all combustible matter, surrounded by those glorious 
manifestations of light and heat which every conflagra- 
tion presents." ■ — Cooke. 

130. Combustion is Self-sustaining. — It is not neces- 
sary to arouse any large amount of oxygen to activity 
in order to insure the continuance of the combustion. 
When, for instance, a lighted match is held to the wick 
of a candle, it excites but a few molecules of oxygen to 
activity. These few rush into combination with the ele- 
ments of the candle, and by so doing develop sufficient 
heat to awaken the activity of more oxygen, which in 



THE CHEMISTRY OF THE ATMOSPHERE. 97 

turn enters into combination and develops more heat. 
In this way a supply of active oxygen is maintained until 
the candle is consumed. 

The slowness of combustion depends upon the fact, 
that the oxygen is mixed with the inert nitrogen in such 
proportions as generally to " restrain the awakened ener- 
gies of the fire-element within the narrow limits which 
man appoints." 

131. The Point of Ignition, — Different substances 
begin to burn at very different temperatures. This is 
well illustrated in the kindling of a coal-fire. Shavings 
are put into the grate first, then kindling-wood, then 
charcoal, and finally hard coal. The shavings are lighted 
by means of a match. The match is a bit of dry, soft 
wood, one end of which is covered with sulphur and 
tipped with phosphorus. It is a well-known fact, that 
when two bodies are rubbed together, heat is developed.- 
On striking the match, sufficient heat is developed by the 
friction to ignite the phosphorus, which takes fire at a 
temperature of about 150 Fahrenheit. The phosphorus 
in burning develops heat enough to ignite the sulphur, 
which burns at a temperature of about 500 . The burn- 
ing sulphur develops heat enough to ignite the wood of 
the match ; the match, to ignite the shavings ; the shav- 
ings, the kindling-wood ; the kindling-wood, the char- 
coal ; and the charcoal, the hard coal, which requires 
the temperature of a full white heat to set it on fire. 

132. The Products of Combustioiz are not always 
Gaseous. — In the burning of coal-gas and of a candle, 
the products are wholly gaseous, and in the burning of 
wood they are mainly gaseous ; but when, metals, as cop- 
per and iron, burn in oxygen, the products of their com- 
bustion are solid. 

133. Magnesium and some other Metals will burn in 
the Air. — A magnesium wire will burn brightly in the 

7 



9& THE CHEMISTRY OF THE ATMOSPHERE. 

air (96). Calcium, also, burns readily in the air (113), as 
aluminium (97) does, if pulverized and strongly heated. 

It will be noticed that all these elements are rare in 
their free state. Many of the rare metals, as potassium, 
sodium, magnesium, and calcium, are as combustible as 
carbon ; but they differ from carbon in giving rise to 
solid products while burning. 

134. Oxygen is not the o?ily Supporter of Combus- 
tion. — If a piece of gold-leaf or Dutch foil be dropped 
into a jar of chlorine, it vanishes in a flash of light (53). 
Here the burning consists in a combination with chlorine. 
Tin and copper foil and pulverized antimony will also 
bum in chlorine. Many metals will burn in the v.apor of 
sulphur ; the burning being then a combination of the 
metal with sulphur. 

135. The Materials erf the Earth' *s Crust are chiefly 
Chemical Compounds. — We have seen that when mar- 
ble is acted upon by muriatic acid (42) we obtain car- 
bonic acid \ C0 2 , and calcic chloride, CaCl. The calcium, 
carbon, and oxygen of these compounds must come from 
the marble, or calcic carbonate, CaC0 3 . 

We find, then, in marble two very combustible sub- 
stances, calcium and carbon, combined with oxygen. 
Limestone has the same composition. Calcium, then, 
which is a very great rarity in a free state, is a very 
abundant element in nature. 

It has been found that the rocks and solid matter of the 
earth are made up chiefly of such combustible elements 
as potassium, calcium, magnesium, aluminium, and car- 
bon, combined with oxygen. Many of the rarest and 
most costly metals, then, are the most abundant in nature. 
The fact that they are so rare in a free state is due to their 
extreme combustibility. It is very difficult to separate 
them from oxygen, and no less difficult to keep them 
separate. 






THE CHEMISTRY OI 



ATMOSPHERE. 



99 



136. The Present Materials of the Earth are Prod- 
ucts of Combtistion. — We see, then, that water, the 
most abundant of liquids, is made up of the very com- 
bustible elements, hydrogen and oxygen ; while the solid 
materials of the earth are composed chiefly of the very 
combustible elements, potassium, magnesium, calcium, 
aluminium, carbon, and silicon, in combination with 
oxygen. These materials are the products of combus- 
tion. There must have been a time when these elements 
existed together in a free state. Then, by some means 
unknown to us, the mass took fire ; and the conflagration 
raged until all the materials were consumed. There was 
more oxygen than was needed for the combustion ; and 
this is now found in the air in a free state. Oxygen was 
the most abundant of all the elements, since it alone 
makes up half the weight of the solid earth, eight-ninths 
the weight of the water, and one-fifth the weight of the 
atmosphere. 

The diagram below (from Cooke) illustrates what has 
been said of the composition of the earth. It will be 
seen, that, of the 6$ elements, 13 alone make up at least 
.99 of its known mass, while the other 52 do not consti- 
tute altogether more than .01. 



Oxygen. 
h 


Silicon. 
i 


Aluminium. 
Magnesium. 
Calcium. 


KNaFeC 


S H CI N | 52 others. 



IOO THE CHEMISTRY OF THE ATMOCPHESE, 



SLOW COMBUSTION. 

137. Partially Active Condition of Oxygen. — We 
have seen (11, 12) that, besides its active and passive 
states, oxygen exists in a third, or intermediate, condi- 
tion, in which it is partially active. In this form it plays 
a very important part in nature. It acts silently and 
slowly, taking months, and even years, to accomplish its 
work ; but the results " far surpass in true grandeur those 
dazzling displays of power which the fire-element mani- 
fests when fully aroused." 

138. Decay. — When wood, or any other organic sub- 
stance (that is, any compound of vegetable or animal 
origin) is exposed to moist air, it decays. It first be- 
comes rotten, and then slowly disappears. This decay 
consists in a gradual union of the substance with oxygen ; 
in other words, a slow combustion. A log of wood 
which rots in the forest undergoes the very same change 
as one which is burnt on the hearth ; the sole difference 
being, that, while the latter burns up in a few hours, the 
former is consumed only after the lapse of many years. 

Wood, like other vegetable compounds, consists mainly 
of carbon, hydrogen, and oxygen. When it burns on the 
hearth, its carbon and hydrogen combine with the oxygen 
of the air, forming carbonic acid and water, which pass 
off in the smoke. The hydrogen is more combustible 
than the carbon, and therefore burns first, leaving the car- 
bon in the form of glowing coals. These are consumed 
in their turn, gradually smouldering away, until nothing 
is left but a little ashes. 

Quite the same process is going on with the decaying 
log in the forest. In decay, as in burning, the hydrogen 
of the wood unites with the atmospheric oxygen sooner 
than the carbon does ; hence, in this stage of its decay, 
the wood becomes darker, and more like charcoal. At 



THE CHEMISTRY OF THE ATMOSPHERE. IOI 

length, both the hydrogen and the carbon are burnt ; and 
the log is slowly converted into carbonic acid and water, 
leaving only a handful of earth as the ashes of this lin- 
gering combustion. Even the heat generated in this 
form of burning is found to be precisely the same as in 
ordinary combustion ; the only difference being that, in 
the latter case, it is all set free in a few hours, while in 
the former it is so slowly developed that it escapes our 
notice, 

139. Causes of Decay. — Green wood decays much 
sooner than dry wood. Indeed, if wood be kept per- 
fectly dry, it will not decay for ages. In the dry climate 
of Egypt, wooden mummy-cases have been preserved 
for more than three thousand years. 

The decay of the green w T ood is due to the presence of 
what are called albuminous substances. The most im- 
portant of these is vegetable albumen, and it is essen- 
tially the same thing as the albumen (or white) of an 
egg. We have said that most vegetable substances are 
made up of carbon, hydrogen, and oxygen ; but these 
albuminous compounds, which form only a small part of 
the bulk of plants, contain an additional element, nitro- 
gen. We have seen that the compounds of nitrogen are 
generally very unstable, and these albuminous substances 
are peculiarly so. In the presence of moisture they soon 
putrefy, or break up into simpler compounds. The 
oxygen of the air takes no part in this process, but, by 
contact with the putrefying substance, it is, in some mys- 
terious way, awakened to the state of partial activity 
mentioned above. It is thus enabled to attack and con- 
sume the wood and all the other organic compounds 
present. The decay, or slow combustion, once begun, is 
self-sustaining ; fresh portions of oxygen being continually 
roused to activity by the process itself, precisely as in 
ordinary burning (130). 



102 THE CHEMISTRY OF THE ATMOSPHERE. 

When the nitrogenized vegetable compounds are 
burnt, the nitrogen passes off in a free state ; when 
they decay, combined with hydrogen as ammonia. 

140. Rusting. — The slow combustion of metals is 
called rusting, and the oxide formed is called rust. All 
the familiar metals, except silver, gold, and platinum, are 
tarnished on exposure to the air ; that is, they become 
covered with a film of rust, or oxide. 

That heat is developed by rusting, as by other kinds of 
slow combustion, is shown by the fact that if a large pile 
of iron-filings be moistened and exposed to the action of 
the air so that they rust rapidly, the temperature rises 
perceptibly. 

A remarkable case of heat developed by rusting oc- 
curred in England during the manufacture of a subma- 
rine electric cable. The copper wire of the cable was 
covered with gutta-percha, tar, and hemp, and the whole 
enclosed in a casing of iron wire. The cable, as it was 
finished, was coiled in tanks filled with water : these 
tanks leaked, and the water was therefore drawn off, 
leaving about 163 nautical miles of cable coiled in a mass 
30 feet in diameter (with a space in the centre 6 feet in 
diameter) and 8 feet high. It rusted so rapidly that the 
temperature in the centre of the coil rose in four days 
from 66" to 79°, though the temperature of the air did 
not rise above 66° during the period, and was as low as 
59° part of the time. The mass would have become even 
hotter, had it not been cooled by pouring on water. 

141. Spontaneous Combustion. — When charcoal which 
has been finely pulverized for making gunpowder is ex- 
posed in large heaps, the oxygen of the air combines 
with it slowly at first ; but, as the heat developed accu- 
mulates, the oxidation becomes more rapid, until in some 
cases the mass takes fire and burns. 

So too, when cotton or tow, which has been used for 



THE CHEMISTRY OF THE ATMOSPHERE. IO3 

wiping- machinery, and has become saturated with oil, is 
laid aside in heaps, it begins to oxidize slowly ; but the 
heat developed makes the combustion more and more 
rapid, until sometimes the heap bursts into a flame. 

This rapid combustion, developed gradually from slow 
combustion, is called spontaneous combustion. 

142. Respiratio?i. — The albuminous or n it rog crazed 
compounds, which form but a small part of the plant, 
make up almost the entire bulk of the animal, so that 
animal substances are even more prone to decay than 
vegetable. And this decay is not confined, as we might 
suppose, to dead animal matter, but is constantly going 
on in the living animal. The only difference is, that in 
the latter case the loss from decay is continually repaired, 
while in the former case it is not. The materials for the 
repair of the living body are furnished by the food. 

This food is mainly made up of three classes of sub- 
stances: (1) non-nitrogenized, as starch and sugar; 
(2) nitrogenized, as lean meat; and (3) fatty sub- 
stances, as butter. All three kinds are absolutely ne- 
cessary to the life of man. They are all contained in 
milk, which may be regarded as " the type of animal 
food." It contains sugar, which belongs to the first of 
the above classes ; caseine, or curd, which belongs to the 
second ; and butter, which belongs to the third. Bread 
also contains all three kinds of food ; being made up of 
(r) starch, (2) gluten (the most important nitrogenized 
constituent of wheat and other grain), and (3) a small 
quantity of oil. A man cannot live for any length of 
time on any one kind of food, as starch or butter, or on 
any mixture of kinds of food, which does not contain all 
three classes of substances. 

The different classes of food serve different purposes 
in the body. The nitrogenized and a part of the fatty 
substances supply the waste which results from the action 



104 THE CHEMISTRY OF THE ATMOSPHERE. 

of the varied machinery of the body. They renew the 
muscles, sinews, and nerves, which are constantly wear- 
ing out. On the other hand, the non-nitrogenized sub- 
stances, as starch and sugar, probably take no part in 
repairing the machinery, but merely furnish fuel to keep 
up the heat of the body. To produce heat they must 
be burnt up, and we shall see that the process is an- 
other example of slow combustion. 

Starch and sugar make up by far the greatest part of 
this fuel, and in fact of our food generally. They are 
almost identical in composition, and starch can readily 
be converted into sugar. When taken into the stomach, 
starch undergoes this change, and the sugar then readily 
dissolves in the water present. The solution is ab- 
sorbed by the veins, and becomes mingled with the 
blood, which carries it to the heart. By the heart, which 
is made up of two force-pumps, the blood is forced 
through the lungs. These are composed of millions of 
little membranous bags or air-cells, closely packed to- 
gether, and all connected by means of tubes with the 
■windpipe, and thus with the nose and mouth. The 
membrane of the cells is very thin, so that they are easily 
compressed. The whole mass of the lungs is also very 
elastic, and by the action of muscles they are alternately 
expanded and contracted as we breathe. When they ex- 
pand, the air from without rushes in and fills the cells ; 
and when they contract, this air is forced out again. 

We have said that the blood charged with sugar is 
forced through the lungs. The tube, or arteiy, which 
conveys it, divides and subdivides, until it is reduced to 
very small capillary tubes, which form a delicate network 
on the surfaces of the air-cells. The walls of these capil- 
laries are very thin, and the oxygen of the air readily 
passes through them, by a process called osmose, and 
mingles with the blood. At the same time, and in the 



THE CHEMISTRY OF THE ATMOSPHERE. 



™5 



same way, carbonic acid is given out by the blood, and 
mixes with the air. The blood, holding in solution both 
sugar and oxygen, now goes back to the heart ; and by 
the second force-pump it is sent to all parts of the body. 
In the mean time, the sugar is burnt up by the oxygen 
which was absorbed in the lungs. 

" Sugar, like wood, consists of carbon, hydrogen, and 
oxygen. The last two are present in the proportions to 
form water, so that sugar may be said to be composed of 
charcoal and water. Of these two substances the char- 
coal only is combustible. This, during the circulation of 
the blood, is slowly burnt up by the dissolved oxygen, 
and converted into carbonic acid, which remains in solu- 
tion until it is discharged, when the blood returns again 
- to the lungs, or else escapes through the skin." * 

Respiration, then, is a kind of combustion, in which 
" the fuel is sugar, and the smoke carbonic acid and 
aqueous vapor." The presence of carbonic acid in the 
air, from the lungs, may be proved by breathing through 
a glass tube into lime-water, which soon becomes milky. 
The presence of the watery vapor may be shown by 
breathing upon any cold substance. 

The weight of carbonic acid breathed out by a full- 
grown man, in a day, varies from i to 3 pounds, or from 
9 to 27 cubic feet ; and the weight of carbon burnt is 
from 5 to 15 ounces. The amount of heat produced is 
of course the same as would be set free by burning the 
same weight of charcoal in a stove. The temperature of 
the body is thus kept above that of the air ; the heat 

* Cooke's "Religion and Chemistry." The greater part of 
§§ I 37 _I 39 and 142-144 has been condensed from the 3d and 4th 
Lectures in this admirable series. We cannot too strongly com- 
mend the book to teachers. They will be certain to draw from 
it, for the purposes of oral instruction, far more largely than our 
limits have permitted here. 



Io6 THE CHEMISTRY OF THE ATMOSPHERE. 

of the blood, even in the coldest climate, being main- 
tained at 96 . 

" In regulating the temperature of his body, man fol- 
lows instinctively the same rules of common sense which 
he applies in warming his dwellings. In proportion as 
the climate is cold, he supplies the loss of heat by burn- 
ing more fuel in his lungs, and hence the statements of 
arctic voyagers, who have told us that twelve pounds 
of tallow-candles make only an average meal for an 
Esquimaux, are not inconsistent with the deductions of 
science." 

143. SIovj and Rapid Combustion of Sugar. — We 
may compare the rapid combustion of sugar in air with 
its slow combustion in the body, by the following ex- 
periment : Take 2 ounces of pulverized sugar, or the 
average quantity burnt in the body of a man in an hour, 
and mix it with 5^ ounces of pulverized potassic chlorate. 
We have then the sugar and the solidified oxygen of the 
chlorate mingled as in the blood ; but the oxygen is pas- 
sive, and will not combine with the sugar, until roused 
to activity. A single drop of sulphuric acid let fall upon 
the mixture serves to awaken its dormant energy ; and 
the mass is consumed in an instant, with intense evolu- 
tion of heat and light. The amount of heat concentrated 
in this momentary burst of flame is no greater than would 
have been generated in the blood in the course of an 
hour. 

" The splendid displays of combustion arrest our at- 
tention by their very brilliancy, while we overlook the 
silent yet ceaseless processes of respiration and decay, 
before which, in importance and magnitude, the greatest 
conflagrations sink into insignificance. These are but 
the spasmodic efforts of nature ; those, the appointed 
means by which the harmony and order of creation are 
preserved." 



THE CHEMISTRY OF THE ATMOSPHERE. IO7 

144. The Daily Consumption of Oxygen in Nature. 
■ — "Faraday has roughly estimated that the amount of 
oxygen required daily, to supply the lungs of the human 
race, is at least one thousand millions of pounds ; that 
required for the respiration of the lower animals is at 
least twice as much as this, while the always active pro- 
cesses of decay require certainly no less than four thou- 
sand millions of pounds more, making a total aggregate 
of seven thousand millions of pounds required to carry 
on these processes of nature alone. Compared with this, 
the one thousand millions of pounds which, as Faraday 
estimates, are sufficient to sustain all the artificial fires 
lighted by man, from the camp-fire of the savage to the 
roaring blaze of the blast-furnace, or the raging flames of 
a grand conflagration, seem small indeed. 

Amount of Oxygen requii'ed Daily, 

Whole population 1,000,000,000 

Animals 2,000,000,000 

Combustion and fermentation . 1,000,000,000 
Decay and other processes . . 4,000,000,000 

Oxygen required daily . . ■=. 8,000,000,000 lbs. 

" How utterly inconceivable are these numbers, which 
measure the magnitude of nature's processes, — eight 
thousand millions of pounds of oxygen consumed in a 
single day ! When reduced to tons, the number is 
equally beyond our grasp ; for it corresponds to no less 
than 3,571,428 tons. If such be the daily requisition of 
this gas, will not the oxygen of the atmosphere be in time 
exhausted ? It is not difficult to calculate approximately 
the whole amount of oxygen in the atmosphere. It is 
equal to about 1,178,158 thousand millions of tons; a 
supply which, at the present rate of consumption, would 
last about nine hundred thousand years." 



io8 



THE CHEMISTRY OF THE ATMOSPHERE. 



THE GROWTH OF PLANTS. 



Fig. 20. 



145. The Embryo Plant in the Seed. — How do 
plants grow ? How does the tiny seed become the leafy- 
herb ? How does the little acorn develop into the giant 
oak ? We shall get the best answer to these questions by 
tracing a plant through its whole growth. 

The seed is formed in the flower, the essential parts of 
which are the stamens and the pistil. Tne stamens 
bear the anthers, and these contain the pollen. The 
pistil is in the centre of the flower. It encloses in its 
ovary the ovules, which, when ripened, become seeds. 

In the ripe seed we find the embryo, which is a mini- 
ature plant with stem and leaves. How has this embryo 
been formed ? 

At a certain time a little cavity is formed in the centre 
of the ovule within the pistil. This cavity is called the 
embryo sac, and is marked s in Figure 
20. Within this sac, at its upper end, 
we see a minute body or vesicle, v. 
This is the first germ of the embryo ; 
but in order that it may begin its de- 
velopment, it must be acted upon by 
the pollen. This we see in the form 
of small grains, a, resting on the top 
of the pistil. It has fallen from the 
anthers, and lodged here ; and now it 
sends out a very fine and delicate tube, 
the pollen-tube, which pierces the tis- 
sue of the pistil, and extends itself 
until it reaches the vesicle, v. Its con- 
tact with this microscopic particle of 
matter has the mysterious power of making it begin to 
grow, and thus form the embryo. 

The vesicle is at first a single cell; that is, a mem 







THE CHEMISTRY OF THE ATMOSPHERE. 



IO9 



branous globule, filled with liquid, in which minute par- 
ticles can sometimes be discerned. After it has been 
acted upon by the pollen-tube, it enlarges somewhat, and 
a partition forms across its interior, dividing it into two 
cells. Each of these grows and divides in like manner, 
and thus a cluster of cells is formed. After a time the 
mass begins to take a definite shape. One end becomes 
the radicle, or the beginning of the root of the plant ; 
and the other divides into two parts, which develop into 
the cotyledons, or seed-leaves. It is now a perfect em- 
bryo, a miniature plant, with root, stem, and leaves, but 
still shut up in the seed. 

146. The Plantlet. — The growth of the plant in the 
seed, and out of the seed, is essentially the same process. 
The same- division and multi- 

Fjg. 21. 

plication of cells continues, and 
all the parts of the plant are 
formed by the clustering or ag- 
gregation of these cells. The 
cells are too minute to be dis- 
tinguished with the naked eye, 
but the microscope shows them 
in every portion of the plant. 
Figure 21 shows a thin slice of 
a rootlet, cut crosswise and 
lengthwise, as it appears when 
highly magnified. We see that the whole structure is 
cellular; that is, made up of cells crowded together. 
A single cell is represented in Figure 22. The natural 
shape of the cell is spherical ; but when cells are clus- 
tered or crowded together, they compress one another 
into the shape in which we see them in these figures. 
Where they are not thus squeezed, they are generally 
found to be spheres, more or less perfect. They vary 
in size, from about the thirtieth to the thousandth of an 
inch in diameter. 




no 



THE CHEMISTRY OF THE ATMOSPHERE. 




At first the cells are all alike in shape and in text- 
ure ; but they are greatly modified in both respects in 
forming the varied tissues of the plant. 
They may be lengthened out into tubes, 
as in the fibres of cotton, which are 
single cells thus drawn out. The soft, 
thin membrane which encloses them may 
become hard and thick, as in the shell o. 
a walnut or the tough wood of an oak. 
They may be closely crowded together, and nearly 
filled up with solid matter ; or they may be loosely 
interlaced, and form vessels to contain the vegetable 
juices. Their contents are as varied as their structure, 
and, seen through the transparent walls, give rise to all 
the manifold colors of leaf and flower and fruit. 

Figure 23 (from Wood's "Class-book of Botany") 
shows a few of the varied forms which cells assume. At 
the top we have wood-cells from the fibre of flax. Below 

Fig. 23. 







are represented the many-sided cells of the pitli of elder ; 
stellate »( star-shaped) cells of the pith of the rush ; spher- 
ical cells of the houseleek ; and wood-cells of the oak. 

147. Organic Structure. — This cellular structure is 
the characteristic of organic beings ; that is, plants and 



THE CHEMISTRY OF THE ATMOSPHERE. Ill 

animals, as distinguished from inorganic things, or 
minerals I and hence it is called organic structure. The 
cell is " the simplest form of organic life," whether vege- 
table or animal. Cells are the units of which the most 
complicated organic tissues are made up. They are es- 
sentially different, then, from the particles into which an 
inorganic or mineral substance may be divided. Each 
of these particles has all the properties of the mass from 
which it was separated ; and if we divide it into yet 
smaller particles, the same will be true of those ; and so 
on indefinitely. But if we cut a cell in two, the halves 
do not have the properties of the whole ; they are not 
smaller units, but the fragments of a unit. 

148. The Food of Plants. — Plants get their food 
from the earth and the air, but much the greater part 
from the air. We know that there are plants which 
flourish in the most barren soil, or even upon the naked 
rock, and that some live and grow suspended in the air, 
and having no contact with the earth. Even those which 
demand a rich soil are indirectly indebted to the air for 
what they draw from the earth. The soil owes its fer- 
tility to the decomposition of organic matter ; and this 
organic matter was originally produced by plants which 
had no rich soil to draw from, but were dependent 
mainly upon the air. 

The atmosphere, then, is the storehouse from which 
plants directly or indirectly obtain nearly all their food. 
The portion which is purely of earthy origin is always 
insignificant, and_ often it is nothing at all. In fact, plants 
give to the earth far more than they get from it. This 
is illustrated by the accumulation of vegetable organic 
matter in the soil wherever vegetation is undisturbed 
from year to year. In uncultivated fields and in pri- 
meval forests we often find a great depth of rich mould. 
The more rank and luxuriant the vegetation, the more 



112 THE CHEMISTRY OF THE ATMOSPHERE. 

rapidly this deposit increases, showing that the plants 
not only restore to the soil all that they have drawn from 
it, but are continually transferring fresh matter from the 
aerial storehouses to the earth. 

But while the soil is enriched by undisturbed vege- 
tation, it is impoverished by agriculture. The farmer 
carries away the crop from the field, with all that it has 
taken from both the earth and the air. The land cannot 
yield in this way year after year, unless he follows the 
example of nature, and restores to the soil an equivalent 
for what he removes. This he can do by the use of 
manure. 

149. The Earthy Portion of the Plant, — If we burn 
wood or any other vegetable substance, almost all of it is 
dissipated into air. But a little ashes will remain ; and 
these represent the earthy or inorganic portion of the 
plant. They consist mainly of alkaline chlorides, potash, 
soda, silica, metallic phosphates, calcic and magnesic 
carbonates, and ferric and manganic oxides. These are 
dissolved in the water which soaks through the soil and 
which is taken up by the roots of the plant. Much of 
the water is evaporated through the leaves, but the sub- 
stances which it held in solution remain behind, and 
thus gradually accumulate ill the tissues of the plant. 

Since the plant must obtain from the soil the inorganic 
materials it needs, it is evident that it will flourish only 
in a soil containing those materials. This explains why 
certain plants thrive only in certain situations. A locality 
may be fertile for some species of vegetation and barren 
for others. The pines, which need little alkaline matter, 
will flourish in a sandy soil containing little alkali ; but 
the maples and elms, which require a good deal of pot- 
ash, cannot live in such a soil. 

We have said that the farmer, who carries away the 
produce of the field with all that it has drawn from the 



THE CHEMISTRY OF THE ATMOSPHERE. 



IJ 3 



soil, must restore in the form of manure an equivalent for 
what he removes, or the field will soon become impover- 
ished. 

U A medium crop of wheat takes from one acre of 
ground about 1 2 pounds ; a crop of beans, about 20 
pounds; and a crop of beets, about 11 pounds of phos- 
phoric acid, besides a very large quantity of potash and 
soda. It is obvious that such a process tends continually 
to exhaust arable land of the mineral substances useful to 
vegetation which it contains, and that a time must come, 
when, without supplies of such mineral matters, the land 
would become unproductive from their abstraction. . . . 
In the neighborhood of large and populous towns, for 
instance, where the interest of the farmer and market- 
gardener is to send the largest possible quantity of pro- 
duce to market, consuming the least possible quantity on 
the spot, the want of saline principles in the soil would 
very soon be felt, were it not that for every wagon-load 
of greens and carrots, fruit and potatoes, corn and straw, 
that finds its way into the city, a wagon-load of dung, 
containing each and every one of trfese principles locked 
up in the several crops, is returned to the land, and 
proves enough, and often more than enough, to replace 
all that has been carried away from it." — Boussin- 

GAULT. 

This renewal of fertility is sometimes attained by let- 
ting the field lie fallow, or uncultivated, for one or more 
years. The inorganic materials of the soil are mainly 
furnished by the gradual disintegration of the rocks; and 
while the field lies fallow this process is going on, under 
the influence of the oxygen and carbonic acid of the air, 
aided by the rains and changes of temperature. In this 
way, fresh portions of the rocks or of their ruins are 
rendered soluble and thus fitted for the nourishment of 
plants. 



114 THE CHEMISTRY OF THE ATMOSPHERE. 

An alternatioiz of crops may answer the same purpose 
as letting the field lie fallow. For instance, wheat and 
potatoes may be raised on the ground in alternate years. 
The wheat requires a large amount of silica and alkaline 
matter, while the potatoes take up no silica. The re- 
newal of the soluble silica in the soil therefore goes on, 
while the potatoes are growing, as it would if the field 
were fallow. 

Some soils abound in silicates so readily decomposed, 
that in every one or two years a sufficient supply for a crop 
of wheat becomes soluble. In Hungary there are large 
districts where wheat and tobacco have been raised alter- 
nately upon the same soil for centuries, the land never 
receiving back any of the mineral matter which is car- 
ried away with the crops. On the other hand, there are 
fields in which the amount of soluble silica required for 
a single crop of wheat is not separated from the insoluble 
masses in the soil in less than three or four years. 

150. The Organic Portion of the Plant. — When 
we burnt the vegetable matter, much the greater part 
of it passed off into me air. This was the organic por- 
tion of the plant. It was taken from the air, and the 
burning has given it back in the very form in which the 
plant found it there. 

We have learned that all the vegetable tissues, how- 
ever varied in their texture and consistency, are almost 
entirely made up of the same kind of cells. The sub- 
stance of which these cells are made is called cellulose^ 
or woody fibre; and it is a compound of carbon, hydro- 
gen, and oxygen, C 12 H 20 O 10 . We have also learned that 
the plant contains small quantities of albuminous com- 
pounds (139), which, in addition to the elements just 
named, contain nitrogen. These four elements, then, 
are essential to the growth of the plant, and must be con- 
tained in its food. 






THE CHEMISTRY OF THE ATMOSPHERE. II5 

151. The Plant gets Hydrogen cmd Oxygen from 
Water. — The hydrogen and the oxygen of the cellulose 

are obtained from the water which the plant takes in, 
not only through its roots, but through its leaves. It will 
be noticed that water contains hydrogen and oxygen la 
the same proportions as cellulose does. 

152. The Plant gets Carbon fro?!! Carbonic Acid. — - 
We have learned that carbon is a solid, and insoluble in 
water. Even if it were reduced to the finest powder and 
mixed with the water, it could not be taken up by the 
plant, since nothing but liquids and gases can pass 
through the walls of the cells. It must, then, be furnished 
to the plant in some liquid or gaseous compound, like 
the carbonic acid, which, as we have seen, is one of die 
gases mixed in the atmosphere. 

Now if a leafy plant be placed under a glass vessel 
and set in the sunshine, and a stream of carbonic acid 
be made to pass slowly over it, it is found that a part of 
the carbonic acid is removed and replaced by oxygen. 
The plant absorbs the carbonic acid, decomposes it, re- 
tains the carbon, and exhales the oxygen. 

We conclude, then, that it is from the carbonic acid 
in the atmosphere that plants get their carbon. In the 
leaves, under the influence of sunlight, the carbonic acid 
is decomposed, the carbon stored away in the plant, and 
the oxygen given back to the air. 

Since carbonic acid is soluble in water, it is probable 
that plants also obtain a part of their carbon through the 
roots. Plants which live under water must get all their 
carbon from the gas dissolved in the water. 

153. The Plant gets Nitrogen from Ammo7tia. — 
We have learned X I2 3) that there is ammonia in the at- 
mosphere, and (37) that this gas is very soluble in water. 
Hence it is washed out of the air by the rain, and, thus 
dissolved in water, is taken up by the roots of plants. 



Iiq THE CHEMISTRV OF THE ATMOSPHERE. 

154. The Growth of Plants is a Chemical Process 
carried on in the Leaf by the Sunlight. — We have 
seen that the plant takes in water, carbonic acid, and 
ammonia ; that it decomposes these substances ; and 
that from their elements it elaborates all the organic 
compounds which enter into its own structure. The 
leaf is the laboratory in which this chemical process is 
conducted, and since it is only in sunshine or bright day- 
light that the work goes on, it is evident that the sunlight 
is the agency by which it is accomplished. 

" The sun's rays, acting on the green parts of the leaf, 
give to them the power of absorbing water, carbonic acid, 
and ammonia, and of constructing from the materials thus 
obtained the woody fibre, starch, sugar, and other com- 
pounds of which the plant consists. We have analyzed 
the woody fibre, and we know that it is composed of 
charcoal and water. Nineteen ounces of wood contain 
nine ounces of charcoal and ten ounces of water. More- 
over, the amount of charcoal required to make nineteen 
ounces of wood is contained in thirty-three ounces of car- 
bonic acid. If, then, we add together thirty-three ounces 
of carbonic acid and ten ounces of water, and subtract 
from this sum twenty-four ounces of oxygen, we shall 
have just the composition of wood. This is what the 
sun's light accomplishes in the leaves of the plant. It 
decomposes the carbonic acid, and unites its carbon to 
the elements of water to form the wood." — Cooke. 

What is here stated to be true of wood is equally true 
of other vegetable products. If in their production car- 
bonic acid and water alone take part, we have such 
substances as woody fibre, starch, sugar, and gum ; and 
these make up nine-tenths of all vegetable structures. If 
the ammonia is likewise employed in the process, Ave 
have nitrogenized products, like albumen and caseine. 

The force which the sunbeam exerts in the decomposi- 



THE CHEMISTRY OF THE ATMOSPHERE. I I ^ 

tion of carbonic acid in the leaf is very remarkable, since 
it overcomes the intense affinity of oxygen for carbon. 

" In order to decompose carbonic acid in our labora- 
tories, we are obliged to resort to the most powerful 
chemical agents, and to conduct the process in vessels 
composed of the most resisting materials, under all the 
violent manifestations of light and heat, and we then suc- 
ceed in liberating the carbon only by shutting up the 
oxygen in a still stronger prison ; but under the quiet 
influences of the sunbeam, and in that most delicate of 
all structures, a vegetable cell, the chains which unite 
together the two elements fall off, and, while the solid 
carbon is retained to build up the organic structure, the 
oxygen is allowed to return to its home in the atmos- 
phere. There is not in the whole range of chemistry a 
process more wonderful than this. We return to it 
again and again, with ever increasing wonder and ad- 
miration, amazed at the apparent inefficiency of the 
means, and the stupendous magnitude of the result. 
When standing before a grand conflagration, witnessing 
the display of mighty energies there in action, and seeing 
the elements rushing into combination with a force which 
no human agency can withstand, does it seem as if any 
power could undo that work of destruction, and rebuild 
those beams and rafters which are disappearing in the 
flames? Yet in a few years they will be rebuilt. This 
mighty force will be overcome ; not, however, as we 
might expect, amidst the convulsion of nature, or the 
clashing of the elements, but silently, in a delicate leaf 
waving in the sunshine." — Cooke. 

155. Plants purify the Air for the Respiration of 
Animals. — We have learned (144) that by the various 
forms of combustion going on in nature, eight thousand 
millions of pounds of oxygen are daily removed from the 
atmosphere ; and that an immense amount of carbonic 



Il8 THE CHEMISTRY OF THE ATMOSPHERE. 

t 

acid is pouring back into the air as one of the chief 
products of this combustion. The atmosphere, then, is 
continually losing the element which is essential to the 
support of animal life, and receiving in its place a gas 
which, even when largely diluted with air, is a deadly 
poison to animals. 

But we have also learned that during the daytime 
plants are constantly drinking in this carbonic acid, and 
giving out an equal bulk of pure oxygen. They are thus 
purifying the air for the respiration of animals. They 
breathe in what animals breathe out, and breathe out 
what animals breathe in ; so that the air is kept in a 
fit state to sustain both forms of organic life. 

An Oriental fable narrates that a nightingale and a 
rose-tree were once imprisoned in a cage of glass, and 
long lived together there, happy in each other's society. 
But at last the rose-tree withered and died ; and the bird 
soon pined away, and perished with grief at the loss of 
its beloved companion. The fancy of the poet is in per- 
fect harmony with the facts of science, and prettily illus- 
trates the dependence of animals upon plants for the very 
breath of life. 

156. PI aitts prepare Food for Animals. — We have 
seen that the plant draws its food directly from the earth 
and the air. It has the power of forming organic com- 
pounds out of inorganic matter. The animal, on the 
other hand, has no such power. It can elaborate its tis- 
sues only from organic matter, which it receives ready- 
made from the vegetable kingdom. It may get this 
matter either directly from the plant, as when it eats 
vegetable food, or, indirectly, as when it eats animal 
food ; but in either case the origin is the same. By 
the process of digestion the organic compounds origi- 
nally prepared by the plant are converted into bones, 
muscles, nerves, or whatever else enters into the struc- 



THE CHEMISTRY OF THE ATMOSPHERE. TI9 

ture of the animal. In this procoss they do not undergo 
any radical change, but merely v ' become parts of more 
finely organized tissues." We find in the blood albumen 
and caseine, having precisely the same composition as 
when prepared from potatoes, and the substance of the 
muscles does not differ essentially from the gluten of 
wheat-flour. 

157. The Relations of Plants and Animals to each 
other and to the Air. — The plant, then, is a producer 
of organic materials ; the animal, a consumer of these 
materials. " While the plant is a true apparatus of re- 
duction, the animal is a true apparatus of combustion, in 
which the substances it derived from the vegetable are 
burnt, and restored to the atmosphere in the form of car- 
bonic acid, water, and ammonia, ready to be again ab- 
sorbed by the plant and to repass through the phases of 
organic life. Our bodies are furnaces, — furnaces con- 
tinually burning, — whose fuel is our own flesh, and the 
smoke of whose fires is the food of the plant. . . . 

" When the foundations of the globe were laid, there 
were collected in the atmosphere all the essential ele- 
ments of organized beings. From this inexhaustible 
storehouse the plant absorbs water, carbonic acid, and 
ammonia, which were placed there for its use, and which 
have been made to serve as its nourishment and food. 
It is the special office of the plant to elaborate from 
these few mineral substances, and a small amount of 
earthy salts, all the materials of organized beings. The 
animal receives these crude materials already prepared, 
and builds with them its various tissues ; but no sooner 
are the cell-walls finished, and the structure ready to dis- 
charge its vital functions, than it is consumed by almost 
the very act which gave it life. The carbonic acid, 
water, and ammonia are restored to the atmosphere, and 
the cycle is complete." — Cooke. 



I2Q 



THE CHEMISTRY OF THE ATMOSPHERE. 



NATURAL VEGETABLE PRODUCTS. 

158. Starch. — Starch has already been mentioned as 
one of the most important products of vegetable growth. 
Its chemical composition is precisely the same as that of 
woody fibre, C^H^O^. It consists of round or oval 
granules, varying considerably in size in different vege- 
tables. The largest are about 2^o tn 5 an< ^ tne smallest 
less than ^Vo tn °f an mcn in diameter. In the potato 
(Figure 24) they are considerably larger than in wheat- 
Fig. 24. Fig. 25. 




flour (Figure 25). These granules consist of concentric 
layers, formed one after another, about a nucleus or 
centre. Lines, indicating these layers, can sometimes be 
seen on the surface of the larger grains, as in those of 
potato starch in the figure. Since the grains from the 
same kind of plant are tolerably uniform in size and 
shape, while they vary much in different species, the 
microscope will show to what plant starch-grains be- 
long. Adulterations of arrowroot, and of other starchy 
substances, may thus be detected. 

Starch is heavier than water, and is insoluble in cold 
water, alcohol, or ether. If, however, it be placed in 
water at 150 , the grains swell up and burst, forming 
a paste or jelly. When long boiled in water, starch 
is converted into the soluble dextri7te (162). 

The test for starch is iodine, with which it forms a 
compound of a deep blue color (60). Bromine gives 
starch a brilliant orange tint. 



THE CHEMISTRY OE THE ATMOSPHERE. 



121 




Fig- 27. 




Starch is the form in which food is stored 
up in the plant for future us 3. In the sssd, it 
furnishes the material for the growth of the 
embryo, before it can draw its nourishment 
from the earth and the air. It sometimes 
surrounds the embryo, as in the seed of the 
onion (Figure 26) ; and sometimes it is 
found in the cotyledons, or seed-leaves, of 
the embryo itself, as in the seed of the bean (Figure 27). 
When the seed germinates, the 
starch is dissolved, and converted 
into dextrine, and this into sugar, 
which is even more soluble. It is 
then dissolved in the sap, which 
conveys it wherever it is needed 
for the growth of the infant plant. 

Several forms of starch are ex- 
tensively used as articles of food. Arrowroot is obtained 
from the roots of a tropical plant, which is cultivated in 
the West Indies, especially in Bermuda and Jamaica, and 
to some extent in the East Indies and in Africa. Tapioca 
is also made from the roots of plants which grow in the 
West Indies, South America, and Africa. Sago is ex- 
tracted from the pith of several species of palm-tree, in 
India and the islands of the Indian Archipelago. Corn- 
starch, maizena, and farina, and various other prepa- 
rations of the kind, are made from the starch of Indian 
corn, wheat, etc. Potatoes yield from 12 to 27 per cent 
of starch ; peas and beans from 33 to 36 per cent ; wheat- 
flour, 56 to 72 per cent ; rye-meal, 61 per cent ; maize, 
81 per cent ; rice, 83 to S$ per cent. 

Starch is also used in large quantities for laundry pur- 
poses ; in the manufacture of cotton cloth, as a sizing for 
the thread ; and in the making of dextrine and grape- 
sugar (161, 162). 



122 THE CHEMISTRY OF THE ATMOSPHERE. 

1-59. Sugar. — Sugar, like starch, is a vegetable prod- 
uct, prepared for the future growth of the plant. It is 
found, dissolved, in varying proportions, in the juices of 
all plants. In ripe fruits it is quite abundant ; pears con- 
taining 6 per cent; peaches, \6\ per cent; and cherries, 
18 per cent. In rye-meal there is about 3^ per cent of 
sugar ; in wheat-flour, from 4 to 8 per cent ; in beet-root, 
from 5 to 8 per cent ; and in dried figs, more than 60 
per cent. 

There are many kinds of sugar, of which the two most 
important are cane-sugar and grape-sugar. 

160. Cane-Sugar. — Cane-sugar, C^H^O^, is found 
in the juices of many plants. It is mostly prepared from 
the juice of the sugar-cane; but on the Continent of 
Europe, it is largely made from beet-juice. In tropical 
regions, it is also manufactured from the juice of the 
date-palm; and in the Northern United States it is 
obtained in considerable quantities from the sap of the 
rock or sugar maple. 

In the manufacture of sugar from sugar-cane, the juice 
is first extracted from the canes by pressure, then mixed 
with a small quantity of slaked lime, and heated nearly 
to boiling*. The lime serves to neutralize the acid in the 
juice, and also to remove the albuminous matter, which, 
if left in the sugar, would soon cause it to ferment and 
spoil. The juice is next evaporated in ©pen pans to a 
thick syrup, which is allowed to cool and crystallize, and 
is then drained in perforated casks. The liquid drained 
off is known as molasses. 

By this process, raw or brown sugar is obtained. 
This is refined by dissolving it in water, adding albumen 
(usually from ox-blood), and heating it. The albumen 
separates most of the impurities from the solution, which 
is then filtered through bone-black to remove the coloring 
matter. It is then boiled down in vacuum pans y large 






THE CHEMISTRY OF THE ATMOSPHERE. I 23 

vessels from which the air is partially exhausted by 
pumps, in order that the evaporation may be carried on 
at a lower temperature than in open pans. By this pro- 
cess there is a saving of fuel, while the quantity of sugar 
obtained is increased. The concentrated syrup is crys- 
tallized in conical moulds, with an opening at the bottom 
for drainage, and thus becomes loaf-sugar. 

When sugar crystallizes very slowly, it forms the large 
and very hard crystals seen in rock-candy. In making 
loaf-sugar, the syrup is frequently stirred, to prevent the 
formation of these large crystals. 

If cane-sugar be heated to about 400 , it loses two 
atoms of water, and is converted into caramel, a dark 
brown substance, much used for coloring brandy and 
other spirits. 

The manufacture of sugar from the sugar-cane, and 
other sources, is now one of the largest branches of 
human industry, but its importance is of comparatively 
modern date. Sugar was known to the Greeks and 
Romans only as a medicine or a curiosity. For several 
centuries after the Augustan age, we find scarcely any 
mention of it ; and, even so late as the seventh century, 
Paul of ^Egina describes it as " India salt, resembling 
common salt in color and consistency, but honey in taste 
and flavor." The sugar-cane appears to have been intro- 
duced into Europe by the Saracens, who cultivated it in 
Rhodes, Cyprus, Crete, and Sicily, in the ninth century. 
In the fifteenth century, it was transplanted into Madeira 
and the Canary Isles, whence it was probably brought to 
America. It became known in England in the fourteenth 
century; and, in 1329, it was sold in Scotland at one 
ounce of silver (equal to four dollars of our money) a 
pound. It did not become an article of ordinary con- 
sumption until the beginning of the seventeenth century. 
Since that time its use has very rapidly increased, and it 



124 THE CHEMISTRY OF THE ATMOoPHERE. 

seems destined to an indefinite extension. "It is so ni> 
tritious, wholesome, and agreeable, that there never can 
be a limit to its use, except in a prohibition or an ina- 
bility to buy it. Men and nations differ widely in respect 
to most kinds of food, sauce, and drinks. Neither wheat, 
rice, flesh, nor potatoes can command unanimous favor. 
No article of housekeeping, save sugar, can be named, 
which is so universally acceptable to the infant and the 
aged, the civilized and the savage." 

The annual production of sugar throughout the world 
is estimated at more than 5,000 millions of pounds, of 
which nearly 88 per cent is cane-sugar ; about 7 per cent, 
beet-sugar ; 4 per cent, palm-sugar ; and about 1 per cent, 
maple-sugar. According to Chambers's Encyclopaedia 
(1867), the yearly consumption for each inhabitant, 
in several great countries, is as follows : Russia, \\ lbs. ; 
Austria, 1^ lbs. ; France, 4 lbs. ; Belgium, 6 lbs. ; Great 
Britain, 30 lbs. ; United States, 40 lbs. 

161. Grape-Sugar . — Grape-sugar, or glycose (less 
properly spelled glucose), C 12 H 24 12 , is found in the juice 
of grapes, plums, cherries, figs, and many other fruits, 
and may often be seen in a crystalline form on raisins 
and dried figs. It likewise occurs in honey. 

It is manufactured on a large scale, in Europe, from 
starch. A mixture of starch and water, at a temperature 
of about 130 , is made to flow gradually into a vat, con- 
taining boiling water, acidulated with one per cent of 
sulphuric acid. In about half an hour, the starch is con- 
verted into sugar. The sulphuric acid is neutralized 
with chalk, forming a deposit of calcic sulphate ; and the 
clear solution of sugar is then boiled down and crystal- 
lized. Instead of starch, in this process, paper, flax, 
cotton and linen rags, sawdust, or any other form of 
woody fibre, may be used. The woody fibre is first con- 
verted into starch, and then into sugar. 



THE CHEMISTRY OF THE ATMOSPHERE. 1 25 

Glycose is largely used in Europe for confectionery, 
for adulterating cane-sugar, and for the manufacture of 
beer and spirits. 

162. Dextrine. — Dextrine, or British gum, C 12 H 20 O 10 , 
is obtained by heating starch to about 400 ; or by sub- 
jecting the starch to the long-continued action of dilute 
acids, at a high temperature. It is often used instead of 
gum-arabic in calico-printing, and for stiffening certain 
goods. It is also applied to the back of postage-stamps 
and other adhesive labels. 

When wheaten bread is baked, a small quantity of 
starch is converted into dextrine on the outside of the 
crust, forming a brownish glazing. 

163. Cellulose and Gun- Cotton. — Celhilose, or woody 
fibre, C 12 H 20 O 10 , has already been described (150). It is 

insoluble in water, alcohol, or ether, but dissolves in an 
ammoniacal solution of cupric oxide (oxide of copper). 

Gun-cotton, or nitro-cellulose, is made by the action 
of strong nitric acid upon cellulose. Cotton w T ool is im- 
mersed, in small portions at a time, in a mixture of equal 
volumes of strong nitric and sulphuric acids. It does not 
undergo any apparent change ; but, on being washed and 
dried, it is found to be very inflammable. Six atoms of 
its hydrogen have been replaced by N0 2 , so that its com- 
position is now represented by C 12 H 14 (NO 2 ) 6 O 10 . 

The use of gun-cotton, as a substitute for gunpowder, 
has been proposed, for the following reasons : — 

(1) The explosive force of gun-cotton is, weight for 
weight, greater than that of gunpowder. (2) The prod- 
ucts of the combustion of gun-cotton, being chiefly car- 
bonic acid and nitrogen, are not so apt to foul the gun. 
(3) When moistened, it becomes inexplosive, and only 
requires drying to render it again explosive. 

The reasons which render the general adoption of this 
substance doubtful are, — (1) its liability to explode on 



126 THE CHEMISTRY OF THE ATMOSPHERE. 

percussion ; (2) the possibility of its spontaneous decom- 
position when kept for a length of time. 

A variety of gun-cotton, containing a smaller propor- 
tion of N0 2 , dissolves readily in a mixture of ether and 
alcohol, and yields a solution termed collodion. This is 
largely used for the purpose of forming a thin coating on 
glass to receive silver salts, upon which the photographic 
image is formed. 

164. Vegetable Parchment. — When paper is im- 
mersed for a short time in a mixture of two volumes of 
oil of vitriol and one o£ water, and thoroughly cleansed 
by repeated washings with water, and finally with am- 
monia, it is changed into a substance resembling parch- 
ment, and often called vegetable parchment. 

" The alteration which takes place in the paper is of a 
very remarkable kind. No chemical change is effected, 
nor is the weight increased ; but it appears that a molec- 
ular change takes place, and the material is placed in a 
transition state between the cellulose of woody fibre and 
dextrine." 

Vegetable parchment is now extensively used instead 
of parchment for legal and other documents. In some 
respects it is preferable to the old kind, for insects attack 
it less. 

165. Vegetable Acids. — The acids of vegetable origin 
are almost innumerable. We shall describe here only a 
few of the most important. 

Tartaric acid, C 4 H 6 6 , is found, either free or com- 
bined with potash or lime, in tamarinds, grapes, pine- 
apples, and many other vegetables. It is usually seen in 
the form of colorless crystals, which have an agreeable 
acid taste, and are soluble in water and alcohol. It is 
used in large quantities in calico printing and dyeing, 
and also in medicine, especially for making effervescent 
draughts. Some of its more important compounds are 



THE CHEMISTRY OF THE ATMOSPHERE. 1 27 

the familiar substances, Rochelle salts, cream of tartar, 
and tartar-emetic. 

Citric acid, C 6 H 8 O t , is usually prepared from lemons. 
It is also contained in gooseberries, currants, raspberries, 
strawberries, and other fruits. It is a crystalline solid, 
readily soluble in water, and has an intensely sour taste. 
It is used in silk-dyeing, in calico-printing, and in 
medicine. 

Malic acid, C 4 H c 5 , is one of the most abundant of 
these vegetable acids. It is found in apples, from which 
(Latin, malum) it takes its name ; in currants, barberries, 
rhubarb, and many other fruits and plants. It forms 
needle-shaped crystals, which are very soluble in water 
and alcohol. It is not used in the arts or in medicine. 

Oxalic anhydride, C 2 O s , is not known in a free state. 
It is found in the juice of wood-sorrel {oxalis acetosclla, 
from which it takes its name), and of many other plants, 
in combination with potash or lime. It forms a com- 
pound with water, H 2 C 2 4 , which is oxalic acid. This 
is a crystalline substance, and is very poisonous. It is 
much used in cotton-printing and straw-bleaching, and is 
prepared in very large quantities by the action of caustic 
potash on sawdust. Crude potassic oxalate (oxalate of 
potash) is thus formed, which, by means of lime, is con- 
verted into the insoluble calcic oxalate (oxalate of lime), 
and this is decomposed by sulphuric acid. 

Tannic acid and tannin are the names given by 
chemists to a number of compounds of C, H, and O, 
which are characterized by a well-marked astringent 
taste. They are soluble in water and alcohol, and form 
precipitates with most metallic oxides. Ferric salts yield 
black, or nearly black, precipitates, which are the basis of 
the ordinary writing inks. Tannic acid also precipitates 
gelatine (or glue) ; and it is by a similar process that it 
converts the gelatinous tissue of raw hides into tanned 



128 THE CHEMISTRY OF THE ATMOSPHERE. 

leather. The bark and leaves of most forest trees, such 
as the oak, elm, willow, horse-chestnut, and pine, and of 
many fruit-trees, as the pear and plum, contain consider- 
able quantities of tannin. Coffee and tea likewise con- 
tain modifications of this compound ; but the tannin in 
coffee, unlike that from all the other plants we have 
named, does not form the black salt with iron. A drop 
of tea on a knife-blade becomes inky at once, but a drop 
of coffee does not. 

1 66. Natural Fats and Oils. — The natural oils and 
fats (fats being merely solid or semi-solid oils) are all 
compounds of organic acids, called the. J~atty acids, with 
a base called glyceri?ie (167), and they arc found in 
both plants and animals. Cocoa-met oil, palm oil, and 
nittmeg bitttcr are examples of vegetable fats. 

The vegetable oils are divided into the Jixed oils, 
which cannot be distilled without decomposition, and the 
volatile oils, which bear distillation without change. 
The Jixed oils are divided into drying and ?ion-drying 
oils. The former become dry and solid from oxidation, 
when spread out thin and exposed to the air ; while the 
latter remain unaltered. The chief drying oils are those 
of linseed, hemp, poppy, and walnut, all much used in 
paints and varnishes ; and the most important non-drying 
oils are olive oil, almond oil, and colza oil, which are ex- 
tensively used in making soap, candles, and illuminating 
oils, in wool-dressing, and for many other purposes. 
Castor oil seems to form a connecting link between these 
two classes of oils, as it gradually becomes hard by long 
exposure to the air. 

The volatile or essential oils are believed to constitute 
the odorous principles of plants. Most of them are nearly 
colorless when fresh, but darken on exposure to light and 
air. When long exposed to the air, they absorb oxygen, 
and become resins. They are largely used in the manu- 



THE CHEMISTRY OF THE ATMOSPHERE. I 29 

facture of perfumery ; for flavoring confectionery and 
liquors, and for various other purposes in the arts ; and 
in medicine. 

167. Soap. — When the oils or fats are boiled with an 
alkali, they undergo the remarkable change called sapon- 
ification. The fat is decomposed into a fatty acid and 
glycerine (166). The acid combines with the alkali to 
form soap, and the glycerine passes into solution. If the 
alkali be soda, a hard soap is formed ; if potash, a soft 
soap. The soaps, then, like the fats, are true salts. 

Fats may also be separated into acid and glycerine by 
distillation with steam, at a temperature between 500 
and 600 \ 

Glycerine (C 6 H 16 O c ), is a colorless viscid liquid, of a 
sweet taste (whence its name, which is from a Greek 
word, meaning sweet), soluble in water and alcohol, but 
nearly insoluble in ether. It is used in medicine, in 
making copying-ink, and as a lubricating agent. 

The most important of the fatty acids are oleic, stearic, 
and palmic, or palmitic. They are used on a large scale 
in the manufacture of candles. 

168. Wax. — The various forms of vegetable wax re- 
semble in many respects the fixed oils, but are quite 
different from them in chemical composition. They are 
solid or semi-solid substances ; easily broken when cold, 
but soft and pliable when moderately warm, and melting 
below 212 . They are insoluble in water and cold 
alcohol, but dissolve readily in ether ; they burn with a 
bright flame, and are not volatile. They are found as 
exudations on leaves and fruits, where they form the 
glaucous surface, which repels water. Some fruits, as 
the bayberry, are thickly coated with wax. 

169. Gums and Resins. — In the strict sense, & gum 
is a substance which dissolves in water, forming a muci- 
lage ; but is insoluble ill ether, alcohol, and oils. A resi?z, 

9 



I30 THE CHEMISTRY OF THE ATMOSPHERE. 

on the other hand, is insoluble in water, and soluble in 
ether, alcohol, and oils. Gum arable and gum Senegal 
are products of different species of acacia, and are exten- 
sively used in the arts. Gum tragacanth is the product 
of a shrub which grows in Persia and Asia Minor. It is 
only partially soluble in water, forming a white paste 
instead of a mucilage. It is used for paste and cement, 
and also for stiffening woven fabrics. Dextrine is now 
much used as a substitute for these and other gums (162). 

The 7'esins are divided into the hard resins, the soft 
resins, and the gum-resins. The hard resins are brittle 
at ordinary temperatures, and are easily pulverized. The 
most important are copal, the varieties of lac, mastic, 
and sa7tdarach. They are much used for varnishes and 
for other purposes in the arts. The soft resins are easily 
moulded by the hand, and some of them are semi-fluid, 
in which case they are called balsams. They consist 
essentially of hard resins dissolved in oils. On exposure 
to the air, .they are oxidized and converted into hard 
resins. Under this head are placed turpentine, Canada 
balsam, etc. The gum-resins are the milky juices of 
certain plants, solidified by exposure to the air. They 
consist of a mixture of gums, resins, and essential oils. 
Caoutchouc, or i7tdia 7'ubber, is the most important of 
the gum-resins. It is obtained from several quite dif- 
ferent kinds of trees. The original india rubber of the 
East Indies is the product of a species of fig-tree. Gutta- 
percha is the dried milky juice of a tree found in Malacca 
and the neighboring islands. The applications of these 
two gum-resins in the arts are almost innumerable, and 
are continually increasing. Many valuable medicines are 
obtained from gums and resins. Amber is a fossil resin. 

170. Vegetable Alkaloids. — A great variety of alka- 
line compounds, known as alkaloids, are produced by 
plants. They are mostly formed in the bark and in the 



THE CHEMISTRY OF THE ATMOSPHERE. 131 

leaves. Among them are some of the most active poisons 
and some of the most valuable medicines, as morphine, 
strychnine, and quinine. Tea and coffee owe their 
peculiar effects to the same alkaloid, theine. Opium is 
remarkable for the great number of these compounds 
Which it contains. The narcotic power of tobacco is due 
to a highly poisonous alkaloid called nicotine. 

171. Proteine Bodies. — Under the term proteine 
bodies have been included the most important nitro- 
genized products of plants, as albumen, caseine, and 
jibri?ie. They all have essentially the same composition, 
containing about 53.6 per cent of carbon, 7.1 of hydro- 
gen, 15.6 of nitrogen, 22.1 of oxygen, and a varying 
quantity of sulphur not exceeding 1.6 per cent. They 
are found in animals as well as in plants, and there are 
several similar compounds found only in animals. 

The proteine bodies form the most essential articles of 
food for animals, since, as we have learned, izitrogcnized 
compounds are indispensable to the repair of the ma- 
chinery of the body. And for these, as for all other con- 
stituents of their food, animals are directly or indirectly 
dependent on plants. 



SUMMARY. 

The atmosphere contains oxygen, nitrogen, carbonic 
acid, and watery vapor, with traces of ammonia and 
nitric anhydride. 

Ordinary combustion, decay, and respiration are chemi- 
cal processes, differing from one another mainly in the ra- 
pidity and the completeness with which they take place. 

The division of substances into combustibles and sup- 
porters of combustion is convenient, though merely con- 



I32 THE CHEMISTRY OF THE ATMOSPHERE. 

ventional ; since combustion consists in the chemical 
union of two or more elements, and, in reality, one of 
the elements is just as combustible as another. 

The present materials of the earth, being mainly com- 
pounds of hydrogen and carbon with oxygen, and of the 
metals with oxygen, chlorine, and sulphur, must be re- 
garded as products of combustion. 

The rusting of the metals is a process of slow com- 
bustion. 

The products of combustion, decay, and respiration 
are chiefly carbonic acid, water, and ammonia. 

The growth of plants is a chemical process, carried on 
in the leaf by the agency of the sunbeam. In growing, 
plants remove from the air carbonic acid, water, and 
ammonia. These compounds are broken up ; the oxygen 
in part given back to the air ; and the other elements, 
with the remaining oxygen, re-arranged so as to form 
the various vegetable compounds. 

By removing the products of combustion, and restor- 
ing oxygen, plants purify the air for the respiration of 
animals. 

Animals derive all their food, directly or indirectly, 
from plants ; while plants derive their food, directly or 
indirectly, from the air. 

Most of the natural vegetable products are compounds 
of carbon, hydrogen, and ,oxygen ; but some contain 
nitrogen in addition to these, and are, therefore, called 
nitrogenized compounds. Of the former class, the most 
important are starch, sugar, dextrine, the vegetable acids, 
the fats and oils, wax, the gums and resins, and the vege- 
table alkaloids ; of the latter class, the proteine bodies, 
including albumen, caseine, and fibrine. The latter are 
the most essential articles of food for animals, since the 
nitrogenized products make up almost the entire bulk of 
the animal structure. 



DESTRUCTIVE DISTILLATION AND 
ITS PRODUCTS. 



172. When vegetable substances are heated in closed 
vessels, so as to exclude the oxygen of the air, they are 
broken up into a number of compounds, which vary with 
the temperature to which they have been exposed. 
When vegetable matter burns or decays, these organic 
compounds, as we have seen, are broken up by the affin- 
ity of oxygen brought to bear upon them from without ; 
while in the other cas? they are broken up by the in- 
ternal action of heat. In the first case, new compounds 
are formed by the addition of new material ; in the 
second case, by subdivision, without any addition of new 
material. The first process is called combustion; the 
second, destructive distillation. 

173. The Preparation of Charcoal. — We have a 
very simple case of destructive distillation in the prepa- 
ration of charcoal. This process may be illustrated by 
putting pieces of dry wood into a flask, closed with a 
cork, through which a glass tube passes. This tube 
passes into a cold glass bottle, and thence to a jar over 
water. Heat the flask, and the wood turns black. 
The jar fills with an inflammable gas. Hold a cold 
glass vessel over ,the flame of this gas, and moisture 
collects upon it, showing that water is a product of the 
burning of this gas. Carbonic acid also is found to 
be produced. This gas obtained from the wood must, 



134 DESTRUCTIVE DISTILLATION. 

therefore, be a compound of hydr6gen and carbon. A 
part of the carbon of the wood combines with hydrogen, 
to form the inflammable gas ; while the greater part re- 
mains behind as a black solid. This black residue is 
charcoal, a form of carbon. If the heating is continued, 
a liquid product is also obtained. 

One way of preparing charcoal is to place billets of 
wood in an iron cylinder, which is closed air-tight and 
heated to dull redness. The volatile products are driven 
off and allowed to escape through a flue, and the solid 
charcoal remains behind. 

A ruder method is practised in the country, where 
wood is plenty. A stake is set in level ground, and 
brushwood heaped about its base. Wood is then stacked 
round the stake, so as to form a mound some 20 or 30 
feet in diameter. This mound is then covered, first with 
leaves or turf, and then with earth, leaving only a small 
opening at the bottom, through which the wood is set 
on fire. When the fire is well under way, the mound is 
covered more deeply and allowed to burn slowly out. 
This requires about a month. The burning of a part of 
the wood furnishes heat for charring the rest. 

174. The Products of the Distillation of Wood. — 
When hard wood, as beech, is subjected to destructive 
distillation in a retort, and the volatile products are 
condensed in a suitable vessel, four principal classes of 
substances are formed: (1) gases; (2) a watery fluid ; 
(3) a dark resinous fluid ; (4) charcoal. 

(1) This product is a mixture of inflammable gases, 
the most important of which are the two hydrocarbons 
(or compounds of hydrogen and carbon), marsh-gas ', 
H 4 C, and olefa?zt gas, H 4 C 2 . 

(2) This product is an acrid liquid, known as ftyro- 
ligneous acid, or wood vinegar, which is used in the 
manufacture of acetic acid. 






DESTRUCTIVE DISTILLATION. 135 

(3) This product is wood tar, a thick liquid, insoluble 
in water, but soluble in alcohol. Its chief use formerly 
was for tarring and calking ships, but recently it has 
become an important source of illuminating and lubricat- 
ing oils. These oils will be described hereafter. 

(4) This product is the charcoal remaining in the 
retort. It is used chiefly as fuel and in reducing metal- 
lic ores. 

175. Ingredients of Wood Tar. — When beech-wood 
tar is distilled, a light oil passes over first, called eupion, 
or wood naphtha. It is now often sold under the name of 
benzole, and used as a burning-fluid, for removing oil- 
stains from clothes, and for countless other purposes. It 
burns with a brilliant white flame, free from smoke ; but 
its extreme inflammability makes it a dangerous liquid 
for lanrps. 

After this light oil has distilled over, a heavy oil fol- 
lows. It contains various ingredients, the chief of which 
are creosote and parajjine. 

176. Creosote. — This is an oily, colorless liquid, with 
a peculiar smoky odor. It has remarkable antiseptic (or 
preservative) properties. A piece of flesh steeped in a 
very dilute solution of it dries up into a mummy-like 
substance, which refuses to decay. Meat, as tongues or 
hams, may be almost instantly cured by dipping it into 
a solution containing one part of creosote to ioo parts of 
water or brine. It is this substance which imparts to 
wood-smoke its property of preserving meat. It is a 
compound of carbon, hydrogen, and oxygen. 

177. Paraffine. — This is a pearly-white, tasteless, and 
odorless solid. The most corrosive acids and alkalies 
have no effect upon it. Hence its name, from parum, 
little, and affinis, from which ajji7tity is derived. 

It burns with a bright white flame, without smoke. It 
is now much employed as a material for candles, which 



I36 DESTRUCTIVE DISTILLATION. 

for purity and lustre are not surpassed by even the best 
wax candles. 

Unsized paper, after having been soaked in paraffine, 
may be kept for weeks in concentrated sulphuric acid 
without undergoing the slightest alteration. Hence it is 
an excellent coating for the labeis of bottles in which 
acids are kept. 

178. Asphalt. — Asphalt, or pitch, is the residue left 
after distilling tar. It is used for varnishes, and as a 
material for making lamp-black. 

179. Slow Destructive Distillation. — When vege- 
table substances decay with a partial or complete exclu- 
sion of air, we have a kind of slow destructive distillation. 
Hydrocarbon gases, which in some places escape from 
the earth in large quantities, are one of the products of 
this process ; the well-known coal-oils are another ; and 
coal is a third. The gas obtained by stirring the mud 
in marshes and at the bottom of stagnant pools is formed 
in this way, and is made up chiefly of marsh-gas, H 4 C, 
and carbonic acid, C0 2 . 

180. The Formation of Mineral Coal. — In tropical 
swamps where vegetation is rank, vast masses of vegeta- 
ble matter accumulate, and gradually decay under water. 
In some cases the land at the bottom of these swamps is 
slowly sinking ; and the bed of peat, as it sinks with it, 
becomes covered with mud and sand, which numerous 
streams are washing down upon it. This goes on, year 
after year and century after century, until the bed is 
buried hundreds of feet beneath the surface. The vege- 
table matter, thus sunk in the earth and subjected to 
enormous pressure, gradually undergoes a process of in- 
ternal combustion similar to that which takes place under 
water. In many cases the decomposition is hastened by 
the agency of the internal heat of the earth. It is proba- 
ble that the vast beds of coal found in various parts of 



DESTRUCTIVE DISTILLATION. I37 

the earth have been thus formed. All this coal is the 
remains of an ancient vegetation, and it undoubtedly re- 
quired millions upon millions of years to complete its 
conversion into coal. 

181. Hard and Soft Coals. — The mineral coals may 
be conveniently divided into hard, or anthracite, and 
soft, or bituminous coal, and there are several varieties 
of each. 

The main differences between the two are these : hard 
coal is almost pure carbon, while soft coal contains also 
considerable hydrogen and some oxygen ; hard coal still 
retains the cellular structure of the wood, which is clearly 
seen under the microscope, while in soft coal this cellular 
structure is almost entirely wanting ; hard coal burns 
without flame, soft coal with flame. 

182. Products of the Distillation of Bituminous 
Coal. — The products obtained by the destructive distil- 
lation of coal are still more numerous than those obtained 
from wood. Wood, containing much oxygen and com- 
paratively little nitrogen, furnishes compounds which 
contain much acetic acid and little ammonia, and which, 
therefore, have an acid reaction. Coal, on the other 
hand, contains much nitrogen and little oxygen, and 
gives products rich in ammonia, and having conse- 
quently an alkaline reaction. 

When coal is distilled at high temperatures, an abun- 
dance of an inflammable gas is obtained, and also a large 
amount of liquid products, which are then called tars. 

When coal is distilled at a low temperature, little gas 
is obtained, and the liquid products are then called oils. 

183. The Composition of Coal-tar. — Coal-tar has 
been found to contain three classes of substances : — 

(1) Acid oils. 

(2) Alkaline oils. 

(3) Neutral oils. 



I3& DESTRUCTIVE DISTILLATION. 

(i) The most important and abundant ingredient of 
the acid oils is carbolic acid, C 6 H e O. It is analogous to 
creosote, and has even more powerful antiseptic proper- 
ties. It is one of the most valuable disinfectants 
known, and both the acid and the compound which it 
forms with lime are now much used for this purpose. 
It is also largely employed in dyeing silk and woollen 
goods. The dye-stuff is prepared by heating carbolic 
acid moderately with nitric acid, and is called picric 
acid. On evaporating this liquid, yellow scaly crystals 
are obtained. Like all the tar colors, its dyeing quali- 
ties, when in solution, are most intense. Silk and wool- 
len goods put into the solution, even when cold, assume 
a rich yellow color, far surpassing that of other dyes. 

(2) The alkaline oils constitute but a small fraction 
of the tar. Their most important ingredients are am- 
monia and aniline, C 6 H 7 N. 

Aniline is an oily substance which, when acted upon 
by compounds which readily part with oxygen, furnishes 
a complete series of the most brilliant dyes. The prep- 
aration of these rich dyes from aniline is one of the 
most interesting discoveries of modern times, and has 
caused almost a revolution in the arts of dyeing and 
calico-printing. It is still more surprising when we con- 
sider that these brilliant colors are obtained from what 
was until recently a disagreeable -waste product of the 
gas-works. When first prepared, they were worth their 
weight in gold ; now, they can be bought at a compara- 
tively moderate price. 

Their dyeing qualities are so intense, that a little ma- 
terial goes a great way ; so that, notwithstanding their 
high price, they are more economical than other dyes. 

(3) The neutral oils are the coal-oils proper. They 
contain a great variety of compounds, both liquid and 
solid, the latter being held in solution. Of the liquids, 



DESTRUCTIVE DISTILLATION. I39 

be7izole, toluole, and cumole are the most important ; and 
of the solids, paraffine and naphthali?ze. 

184. Benzole and JSfitro-benzole. — Benzole is a very 
important compound, as it is the material from which 
aniline is usually prepared. The symbol for benzole is 
C 6 H 6 . When mixed with concentrated nitric acid, it 
loses one atom of H, and takes one of N0 2 in its place, 
and becomes nitro-benzole, C 6 H 5 N0 2 . 

Nitro-benzole is the artificial oil of bitter almonds, 
and is much used in the art of perfumery. Its most im- 
portant use, however, is in the preparation of aniline. 
When heated with acetic acid (C 2 H 4 2 ) and iron filings, 
it loses two atoms of oxygen and takes up two of hydro- 
gen, and is converted into aniline, C 6 H 7 N. 

185. Toluole and Cu7nole. — Toluole, C 7 H 8 , and 
cumole, C 9 H 12 , are the chief ingredients of the well- 
known illuminating or lamp oils obtained from coal. 

186. Naphthaline. — Naphthaline is a beautiful, pearly- 
white solid." It is inflammable, but burns with a smoky 
flame and a disagreeable odor. Brilliant red and blue 
colors, rivalling those prepared from aniline, have lately 
been obtained from this solid. 

When vegetable matter is distilled at a high temper- 
ature, benzole and naphthaline are formed in great abun- 
dance, with but small quantities of toluole, cumole, and 
paraffine. When, on the other hand, the distillation is 
conducted at a low temperature, toluole, cumole, and 
paraffine are formed in large quantities, with but little 
benzole and naphthaline. 

COAL-OILS. 

187. At the beginning of the present century, the 
means of lighting our dwellings consisted, in the main, 
of poor tallow candles and dim and dirty oil-lamps. On 



14O DESTRUCTIVE DISTILLATION. 

the continent of Europe, whale-oil and other animal oils 
were costly, and resort was had to natural tar and bitu- 
minous slate, in order to obtain illuminating oils. For 
more than twenty years past, lamp-oils have there been 
extensively prepared from wood, rosin, and bituminous 
matter. 

In Great Britain and in this country the manufacture 
of coal-oils is of much more recent growth, because the 
extensive whale-fisheries supplied all the wants of the 
market. 

The manufacture of coal-oil was introduced into this 
country in 1853, and was at first confined to those dis- 
tricts where bituminous coal could be mined at a cheap 
rate. 

Soon after this manufacture was established in this 
country, and after the value of coal-oils came to be fully 
recognized, attention was drawn to petroleum, or rock- 
oil, as a ready means of supplying these oils cheaply. On 
examination, this oil was found to be analogous, in its 
composition and its properties, to that obtained by the 
destructive distillation of soft coal and other bituminous 
substances. 

188. The Origin of Petroleum. — All scientific men 
are agreed that the petroleum found in the earth results 
from the decomposition of organic matter, and nearly all 
are agreed that it results mainly from the decomposition 
of vegetable matter. It is, however, a disputed point, 
whether it results from the original decomposition of the 
vegetable substances, or from the action of the internal 
heat of the earth on the bituminous coal at a subsequent 
period. 

It is probable that the petroleum now found in the 
earth is the product both of the original decomposition 
and of subsequent distillation. Petroleum is, however, 
rarely found in contact with bituminous strata of any 






DESTRUCTIVE DISTILLATION. 141 

kind. It is more often found in fissures in sand rocks ; 
rocks in which no oil could ever have been generated, 
since whatever organic matter they might have contained 
was too much exposed to atmospheric oxygen to admit 
of its being bitumenized, or made bituminous. It is not 
only impossible that the oil could have originated in these 
sand rocks, or in the sandy shales which underlie them 
in the oil region in Western Pennsylvania ; but it is most 
probable that the oil ascended from still lower rocks in 
the form of vapor, which condensed in the cavities above. 
Since, then, petroleum is seldom found where it origin- 
ated, but, ordinarily, in cavities of rocks higher up, it 
seems probable that it is mainly the product of distil- 
lation. 

The chemical conditions essential to the generation of 
oil have evidently existed over a very wide area ; but the 
oil is found only where fissures exist in the rocks. These 
fissures serve two purposes : one, to give space for the 
formation and expansion of the hydrocarbon vapor ; the 
other, to furnish receptacles for the condensed oils. 
These fissures must connect with the sources of the oik 
If they have any outlets at the surface of the earth, by 
which the more volatile portions of the oil may escape as 
gas, the oil within them becomes thicker and heavier. 
Hence, as a general rule, the oil found near the surface 
is heavy, the cavities containing it being likely to have 
outlets. It may, of course, happen that a deeply-seated 
fissure has such an outlet. 

189. How Petroleum is obtained. — The oil is ob- 
tained by piercing one of these cavities by a well. It 
often happens that the upper part of the cavity is filled 
with pent-up uncondensible gases. In this case, if the 
well happens to pierce the lower part of the cavity, the 
expansive force of the confined gases will drive the oil 
from the well in a continuous stream. Oil is often forced 



I42 DESTRUCTIVE DISTILLATION. 

from a new well with such velocity, that it rises in a jet 
a hundred feet high. 

It sometimes happens that the lower part of the cavity- 
is filled with brine, upon which the oil floats. If, in this 
case, the well pierces the lower part of the cavity, brine 
is the first product. After a time the salt-well may 
change to an oil-well. 

COAL-GAS. 

190. The Manufacture of Coal-Gas. — The idea of 
turning hydrocarbon gases to the practical purposes 
of illumination occurred at about the same time to 
Murdock, in England, and Lebon, in France. This was 
in 1790; but for a long time there was a strong popular 
feeling against the new light. In England, it was not 
until 1 Si 2 that Parliament consented to charter a com- 
pany for its manufacture. Even then the enterprise was 
looked upon as so visionary, that the act of incorporation 
was said to be granted in order to make a great ex- 
periment of a plan of such extraordinary novelty. In 
December, 1813, Westminster Bridge was first lighted 
with gas. From this time gas-lighting made the most 
rapid progress in England ; and now the consumption of 
gas in London alone amounts to more than seven billions 
of cubic feet annually. To make this gas, eight hundred 
thousand tons of coal are required ; while the length of 
the main pipes in the streets of the city is more than two 
thousand miles. 

Paris was first lighted with gas in 1820. There, as in 
England, strong prejudices had to be overcome. 

The most essential parts of the apparatus used in the 
making of coal-gas are represented in Figure 28. 

Of course, it is only soft or bituminous coal that can 
be used for making gas. This coal is distilled in long 



DESTRUCTIVE DISTILLATION. 



H3 



iron retorts, seen at the left of the figure. When charged 
with coal, these retorts are closed air-tight. They are 




then heated to a very high temperature by the furnaces 
beneath. 



144 DESTRUCTIVE DIST1LLATIOIT. 

The gaseous and volatile compounds, formed by £is 
distillation of the coal, pass up through pipes (one of 
which may be seen leading from each retort) into a long 
horizontal pipe, Jll, called the hydraulic main. This is 
half full of water, into which the pipes from the retorts 
dip. The gas readily escapes from the pipes by bub- 
bling up through the water ; but, of course, it cannot 
return through the water. 

The gas is carried from the hydraulic main through a 
pipe into a tank, T, called the tar cistern. By this time 
the more condensable gases have become liquid, and 
collect in the smaller vessel into which the pipe passes, 
and from which they overflow into • the larger tank. 
From the latter they are drawn off at intervals. These 
condensed products are coal-tar and a liquid highly 
charged with ammonia, called ammoniacal liquor. 

The uncondensed gases pass on through the series of 
upright pipes at C, called the condenser. Here they 
become still further cooled, and all the remaining con- 
densible gases are reduced to the liquid state. 

After leaving the condenser, the gas still contains, be- 
sides the compounds fit for illuminating purposes, the 
noxious compounds carbonic acid and hydric sulphide 
(49). These are removed in the purifier, P. It con- 
sists of a chamber with several perforated shelves, which 
are covered with slaked lime. In passing over this lime, 
the carbonic acid and hydric sulphide are absorbed, while 
the purified gas passes along into the gasometer, G. 

This gasometer consists of a large sheet-iron bell-jar, 
which dips into a cistern of water. The latter is deep 
enough to allow the bell to be completely submerged, 
and filled with water. The bell is counterpoised with 
weights, and rises as the gas enters it. 

From the gasometer the gas passes out, by the pipe 
at the right, into the streets and houses of the city. 



DESTRUCTIVE DISTILLATION. 



ILLUMINATION. 



45 



191. Nature of JFlame. — We know that coal-gas 
barns with flame, while the solid carbon burns without 
flame. All combustible gases burn with flame. 

We have seen that wood, when heated in a closed tube, 
gives oiT an inflammable gas ; and the same is true of 
wax or tallow heated in the same way. Every solid 
which appears to burn with flame can thus be converted 
into an inflammable gas by means of heat. When these 
solids begin to burn, the heat developed is sufficient to 
generate this inflammable gas. It is this gas, and not 
the solid, which burns with flame. 

Flame, then, is gas burning. 

192. A Solid a?id Heat are necessary to Illumin- 
ation. — The oxy-hydrogen flame (22) develops intense 
heat, but scarcely any light. If, however, a cylinder of 
lime be held in this flame, we get the brilliant calcium, 
or Drummo7id light. 

We see, then, that a solid and an intense heat are 
necessary to illumination. (See Appendix, VI.) 

193. These two Conditions are fulfilled in the Burn- 
ing of Coal- Gas. — Illuminating gas, as we have seen, 
is a compound of carbon and hydrogen. If we hold a 
cold glass rod in a gas-flame, it becomes blackened with 
soot, showing that there is free carbon in the flame. We 
therefore conclud3 that the hydrogen of the gas combines 
with the atmospheric oxygen first. In doing so, it de- 
velops great heat. 

In the manufacture of charcoal, the delicate cells of 
the wood are preserved intact ; showing that the car- 
bon, at the high temperature to which it is exposed 
in the process, has no disposition to melt. Its infusi- 
bility is its most marked characteristic (41). 

10 



I46 DESTRUCTIVE DISTILLATION. 

When the hydrogen of coal-gas combines with the 
oxygen of the air, the carbon is set free in a solid state. 
As the hydrogen consumes all the oxygen in the nearest 
layer of air, the carbon must delay a moment in the flame 
before it can get at oxygen to unite with. This finely 
divided solid thus becomes heated white-hot, and gives 
out light. This condition lasts but an instant. The next 
instant the carbon combines with atmospheric oxygen, 
and passes off as a colorless gas. As fast, however, as 
the carbon is consumed, a fresh supply is set free, and 
thus the light is constantly kept up. 

The value, then, of coal-gas for illumination depends 
upon a most delicate adjustment of affinities. 

Were the affinity of carbon for oxygen a little stronger 
than it now is, the carbon would burn at the same time 
with the hydrogen, and there "would be no light in the 
flame. On the other hand, were the affinity of carbon 
for oxygen less than it is, the carbon would not burn at 
all, but, after developing light, would pass away from the 
flame in the form of soot. 

194, Bunserfs Lamp, — T\\Q fact that carbon must 
Fig. 29. remain an instant in the flame in the 

solid state to develop light, is illustrated 
-by Bunsen's burner. It is shown in Fig- 
ure 29, and consists of a brass tube, near the 
bottom of which are four round holes, 
through which the air can pass into the 
tube. A second tube opens into the inside 
of the brass tube from the bottom, just 
on a level with these holes. The coal-gas 
passes into the larger tube, through this 
second tube. The air passes in through the holes at 
the same time, and the two gases become intimately 
mixed before they reach the top of the tube. Upon 
lighting the mixture as it escapes from the tube, it burns 




DESTRUCTIVE DISTILLATION. 147 

with scarcely any light, but a good deal of heat. If we 
close the holes at the bottom of the tube, the gas burns 
with the ordinary luminous flame. In the first case, 
there is an excess of oxygen mixed with the coal-gas, 
so that there is enough to combine "with the carbon as 
soon as it is set free, before it becomes sufficiently heated 
to develop light. In the second case, the carbon cannot 
get at the oxygen to combine with it, until it has passed 
through the burning layer of hydrogen, and thus become 
intensely heated. 

195." The Best Shape for a Gas -Flame. — From 
what has been said, it is evident that the light of the 
flame is developed only at the surface, in the burning 
layer of hydrogen. The ordinary gas-burner is so made 
that the flame will be flat, in order that it may have as 
much surface as possible. The greater the surface, the 
greater the light developed. 

196. The Argand Burner. — A sheet of paper will 
evidently present to the air just as much surface when it 
is bent round till the two edges meet, as when it is flat ; 
while in the second case it is in a more compact form. 
So the ordinary gas-flame will present just as much sur- 
face, if its edges are bent round till they meet. In the 
Argand burner, this form is given to the flame, by sup- 
plying the gas through a circle of small holes in a hol- 
low brass ring. A current of air passes up through this 
ring, furnishing oxygen to the inner surface of the flame. 

197. The Bude Light. — If the interior of the ring of 
an Argand burner be closed, the flame becomes of a dull 
red color. Since no oxygen is supplied to the inner 
surface of the flame, the combustion is imperfect, and 
develops but a low degree of heat. 

If, on the other hand, a stream, of pure oxygen be sup- 
plied to the interior of the cylindrical flame, the flame 
diminishes in size ; but the light becomes very intense, 



I40 DESTRUCTIVE DISTILLATION. 

and of a pure white color. The increased supply of oxy- 
gen increases the energy of the combustion of the hydro- 
gen, and the intensity of the heat developed by it. In the 
first case, the carbon is heated only to a dull redness, 
while in the second case it is raised to a full white heat. 

198. A. Burning Ca?zdle is a miniature Gas -Fac- 
tory. ■ — We have seen that wax or tallow, when heated 
in a flask, is converted into an inflammable gas. This 
gas, in burning, produces water and carbonic acid ; 
hence it must contain hydrogen and carbon, which are the 
main ingredients of coal-gas. This gas is in fact identical 
with coal-gas. The heat of the burning match converts 
some of the wax of the candle into gas, which takes fire, 
and in burning develops sufficient heat to convert more 
of the wax into gas ; and thus the supply is kept up. 

199. The Flame of a Caitdle consists of three dis- 
tinct Parts. — In the flame of a candle there are three 
distinct parts: (1) the dark central zone, or supply of 

Fig. 30. unburnt gas surrounding the wick ; (2) 

the luminous zone, or area of incom- 
plete combustion ; and (3) the non- 
luminous zone, or area of complete 
combustion. If we put one end of a 
small glass tube (see Figure 30) into 
the dark central zone, the unburnt gas 
will pass up the tube, and may be 
ignited at the other end. In the lumi- 
nous part of the flame, as in the case 
of the gas-flame (193), the gas is not 
completely burnt, and carbon is sepa- 
rated in the solid state ; and it is this carbon heated 
white-hot which renders the flame luminous. In the 
outer zone the supply of oxygen is greater ; all the carbon 
is at once burnt to carbonic acid, and the flame here 
becomes non-luminous. 




DESTRUCTIVE DISTILLATION. I49 



SUMMARY. 

Vegetable compounds may be broken up by destruc- 
tive distillation. 

In the preparation of charcoal, wood is decomposed 
into carbon and a number of volatile compounds. 

When these volatile products are cooled and con- 
densed, we obtain : (1) permanent gases ; (2) a watery 
fluid ; (3) a dark resinous fluid. 

(1) The permanent gases are chiefly marsh-gas, H 4 C, 
and olcjiaitt gas, H 4 C 2 . 

(2) The chief ingredient of the watery fluid is pyrolig- 
neous acid, or wood vijiegar. 

(3) The dark liquid is wood tar. 

The most important ingredients of wood tar are wood 
naphtha, creosote, parajjine, and asphalt. 

Mineral coal has probably been formed by the gradual 
decomposition of vegetable matter buried in the earth, and 
thus excluded from the air ; the decomposition in many 
cases being hastened by the internal heat of the earth. 

When the volatile products were allowed to escape 
freely, anthracite coal was formed ; when they could not 
escape, bituminous coal was formed. 

The volatile products often escaped into large cavities 
in the rocks, and on condensing gave rise to the cele- 
brated rock-oil, or petroleum. 

In some cases, this oil may have been formed by the 
decomposition of the vegetable matter at a temperature 
too low for its conversion into vapor, and may afterwards 
have been distilled by the internal heat of the earth. 

The products of the destructive distillation of bitumi- 
nous coal are more numerous than those of the distilla- 
tion of wood. They are less rich in compounds containing 
oxygen, but richer in those containing nitrogen. 



I50 DESTRUCTIVE DISTILLATION. 

When the coal is distilled at a high temperature, a 
large amount of gas is obtained, and the liquid products 
are then called tars. When the coal is distilled at a low 
temperature, only a small amount of gas is obtained, and 
the liquid products are called oils. 

When the gas obtained by the distillation of coal is 
purified, it forms the well-known illuminating gas. 

The most important ingredients of coal-tar are carbolic 
acid, ammo7iia, aniline, be?izole, toluole, cumole, par- 
affine, and naphthaline. 

The anili?ie colors are prepared chiefly from benzole. 

Only gases burn with flame. Solids that appear to 
burn with flame are first converted into a gas by heat, 
and this gas burns with flame. 

The two conditions essential to illumination are the 
presence of a solid and intense heat. 

The illuminating gases are all hydrocarbons, or com- 
pounds of hydrogen and carbon. 

The hydrogen has the stronger affinity for oxygen, and 
burns first. The carbon is set free in a solid state, and 
delaying for an instant in the intense heat of the flame, 
before combining with oxygen, becomes luminous. 

The light of the flame is increased (1) by increasing 
the surface of the flame, as in the ordinary gas-flame, 
and that of the Argand burner ; and (2) by increasing 
the intensity of the combustion of the hydrogen, as 
in the Bude light. 

The heat of the flame is increased by mixing oxygen 
with the gas before it burns, so that the carbon and hy- 
drogen may burn together, as in the Bunsen burner. 

The burning candle or oil-lamp is a miniature gas- 
factory. 

The candle flame consists of three parts : (1) an inner 
zone of unburnt gases, surrounded by (2) a luminous 
zone of incomplete combustion, outside of which is (3) a 
non-luminous zone of complete combustion. 



FERMENTATION. 



200. Causes of Ferme?itation. — Complex organic 
compounds are often broken up into simpler compounds 
by the agency of growing- plants. This process is called 
fermentation, and the organisms which effect it are 
c^W^di ferments. Different ferments give rise to different 
products, as alcohol, vinegar, etc. Most of these fer- 
ments are plants, but one at least is an animal ; and this, 
strange to say, cannot live in contact with free oxygen, 
but flourishes in an atmosphere of hydrogen. In order 
that the ferment should grow, it must be supplied With 
proper food, especially with ammoniacal salts and al- 
kaline phosphates. These are contained in the albu- 
minous matter generally present in the liquid about to be 
fermented. In order that the fermentation should go on 
well, the temperature should be from 70° to 100 ; at 
much higher, as at much lower temperatures, the vitality 
of the ferment is destroyed. 

In many cases, spontaneous fermentation sets in with- 
out the apparent addition of any ferment : thus wine, 
beer, milk, etc., when allowed simply to stand exposed 
to the air, become sour or otherwise decompose. These 
changes are, however, not effected without the presence 
of vegetable or animal life, and are true fermentations. 
The sftorules, or seeds of these living bodies, are al- 
ways floating in the air, and on dropping into the liquid 
begin to propagate themselves, and in the act of growing 
evolve the products of the fermentation. If the liquid 



I5 2 FERMENTATION. 

be left only in contact with air which has been passed 
through a red-hot platinum tube, so that the living 
sporules are destroyed ; or if the air be simply filtered 
by passing through cotton- wool, so that the sporules are 
prevented from coming into the liquid, it is found that 
the liquid may be preserved for any length of time with- 
out undergoing the slightest change. 

The principal forms of fermentation are — 
(i) The alcoholic fermentation, producing chiefly al- 
cohol and carbonic acid. 

(2) The acetous fermentation, producing acetic acid. 

201. Alcoholic Fei-meiztation. — Grape-sugar, if dis- 
solved in presence of yeast (which is a plant and a fer- 
ment), undergoes fermentation, evolving mainly alcohol 
and carbonic acid : — 

Q2 H 24°i2 = 4C 2 H 6 (alcohol) + 4 CO a . 

If cane-sugar be used, it takes up water and is converted 
into grape-sugar (C 12 H 22 O n -f- H 2 = C 12 H 24 12 ), which 
is decomposed as above. The alcoholic fermentation is 
best effected at a temperature between 77 and S6°. 

When the cereal grains are used for making alcohol, 
tire starch of the grain is first converted into sugar. This 
change may be brought about by the action of sulphuric 
acid, as already explained (161) ; but, practically, it is 
usually effected by means of diastase. 

202. The Formation of Diastase in Growing" Plants. 
— We have learned that the seed contains a supply of 
starch which is the food of the embryo plant until it is 
able to derive its sustenance from the earth and the air. 
We have learned, too, that this starch must be converted 
into sugar, in order that it may be dissolved in the sap of 
the plant and carried where it is needed for the purposes 
of growth. Let us now see how the starch is changed to 



FERMENTATION. 



^3 



sugar. The seed contains more or less of the nitrogen- 
ized compound, gluten (142). This, under the influence 
of heat and moisture, begins to putrefy, and Fig. 31. 

a portion of it is converted into the ferment 
diastase. This has so powerful an action 
upon starch, that one part of it, at a tempera- 
ture of 150°, is sufficient to convert 2000 parts 
of starch into dextrine and then into sugar. 

We can now understand how a seed, like 
the acorn (Figure 31), germinates. If we 
cut the acorn open, we see the radicle (at the 
right in the figure), and the two thick coty- 
ledons, or seed-leaves, containing 
the starch and gluten. In the moist 
warm soil the acorn absorbs a little 
water, and the gluten is thus 
changed into diastase, which con- 
verts some of the starch into 
sugar. The radicle absorbs 
this sugar, and uses it to make 
woody fibre. It is thus en- 
abled to thrust out a little root 
and begin to draw food 
from the earth, as well 
as from the starch in the 
seed. It next sends out 
the plwnule, a little stem 
with its first leaves 
unfolding to the /^^- 
air and light. It Up-__ -^ has now the means of 
deriving its nour- ^^^ ishment both from the 
earth and the air, and is no longer dependent upon the 
seed, which soon withers and perishes. Both root and 
stem are now rapidly developed (145-154), and thus at 
length the acorn becomes the mighty oak. 




154 FERMENTATION. 

203. Brewing. — The brewer avails himself of this 
natural change in the germinating seed, and calls into 
action on a larger scale the chemical influence of diastase. 
The grain commonly used for the purpose is barley. 
This is first moistened in heaps, and spread out in a dark 
room to heat and sprout. When the gluten has begun to 
be transformed into diastase and the starch into sugar, so 
that the germ is about to burst from the envelop of the 
seed, the growth is arrested by heating the grain, and 
thus killing the embryo plant. 

The malt, as the barley is now called, is next bruised, 
and soaked in warm water in the mash-tub. The water 
dissolves first the sugar which has already been formed 
in the seed, and then the diastase. The latter acts upon 
the rest of the starch of the seed, and of any raw grain 
which may be added to the malt, converting it into sugar, 
so that little, except the husk of the grain, is left undis- 
solved ; and the liquor, or wort, has a decidedly sweet 
taste. 

The wort is now heated to boiling, to stop the action 
of the diastase, and to coagulate the albumen which has 
been dissolved out of the grain. At the same time, hops 
are added to the wort ; and these, besides giving a bitter 
aroma to the liquid, help to clarify it. The boiled liquor 
is then filtered, and drawn off into shallow vessels, where 
it is cooled down to about 6o°. Yeast is now added, and 
the mixture is allowed to ferment for six or eight days. 

This fermentation is never allowed to continue until 
all the sugar is converted into alcohol. From one-half 
to three-fourths of it is decomposed ; and the rest is left 
to give a sweet taste to the beer, and also to keep it 
from souring in the cask. 

The liquor is next put into casks, where it goes through 
a second and much slower fermentation, which is essen- 
tial to its preservation. When this fermentation is com- 



FERMENTATION. 1 55 

pleted, the cask must be closed tight, to exclude the air, 
the oxygen of which would cause acetous fermentation. 
During this second fermentation, the carbonic acid is 
generated, to which the liquor owes its sparkling effer- 
vescent character. 

204. The Distillation of Spirits. — When fermented 
liquors are boiled, the alcohol they contain rises in the 
form of vapor, mingled with steam. If the boiling be 
performed in a close vessel, and the vapors be led by a 
pipe into a cold receiver, they condense into a liquid, 
containing a large percentage of alcohol. This process 
is called distillatio7i, and the apparatus for carrying it 
on is called a still. 

If the alcoholic liquor thus obtained be re-distilled, or 
rectijied, a spirit may be obtained, containing 90 per 
cent of alcohol and 10 of water. This is the strongest 
commercial alcohol. If this be mixed with calcic chlo- 
ride, which has a strong affinity for water (113), and then 
be re-distilled, pure or absolute alcohol may be obtained. 

We have seen that, in making beer, the fermentation 
of the wort is checked before all the sugar is converted 
into alcohol. But, in the manufacture of spirits from 
grain, the fermentation is prolonged until all the sugar is 
transformed into alcohol and carbonic acid. To leave 
any of it unchanged, would not only involve a loss of 
spirit, but, during the subsequent distillation, might in- 
jure the flavor of the spirit obtained. 

The alcohol obtained from the fermentation of sugar is 
sometimes called -wine alcohol, or vinic alcohol, to dis- 
tinguish it from a large number of similar compounds, 
known to chemists as alcohols. Its symbol is C 2 H e O. 

205. Ether. — When equal weights of strong alcohol 
and oil of vitriol are boiled in a retort, a colorless, fra- 
grant, and highly volatile liquid passes over, called ether, 
or sulphuric ether, C 4 H i0 O. It is called sulphuric 



I56 FERMENTATION. 

ether, to indicate its origin, and to distinguish it from 
other analogous compounds called ethers. 

When poured on the hand, ether produces a strong 
sensation of cold, owing to the rapidity with which it 
evaporates, rendering heat latent. It is very inflam- 
mable, and burns with a white flame. Its vapor forms 
explosive mixtures with air or oxygen. It dissolves oils, 
fats, and resins far more readily than alcohol does. It 
also dissolves sulphur, phosphorus, and iodine. When 
inhaled in sufficient quantity, its vapor is an ancesthetic, 
and was the first substance used for that purpose by 
physicians. 

Acetic ether is obtained by distilling a mixture of 
alcohol, sulphuric acid, and acetic acid. It is used in 
medicine. If nitric acid be used, we get nitric ether, 
which is w T ell known under the name of sweet spirits 
of nitre. Several of the ethers exist in a natural state 
in fruits, giving them their peculiar flavors. 

206. Acetic Acid. — If alcohol, diluted with water, 
be mixed with a ferment, as yeast, and exposed to the air 
at ordinary temperatures, it is soon converted into acetic 
acid, or vinegar. The alcohol absorbs 2 atoms "of oxy- 
gen, forming water and acetic acid :- — 

C 2 H s O + 2 =:H 2 + C 2 H 4 2 (acetic acid). 

This process constitutes what is commonly called the 
acetous fermeiztation. Since the alcohol is oxidized, it 
is in a certain sense a combustion that takes place. It is, 
however, brought about by the influence of a ferment, 
known as the vinegar-plant, or mother of vinegar. 

There are a great many methods of making vinegar on 
the large scale ; but, for the most part, they are only dif- 
ferent devices for exposing to the air as large a surface as 
possible of the alcoholic mixture. In one process, the 
liquid is allowed to trickle down through vats, filled with 



FERMENTATION. 157 

flat pieces of wicker-work, piled one upon another. 
These are first watered with vinegar, or liquid partially 
converted into vinegar, and thus become covered with 
the germs of the vinegar-plant. Air is admitted through 
holes in the bottom of the vats, and passes out at the top, 
after giving up a part of its oxygen to the alcohol. Heat 
is produced by the oxidation, and this causes an upward 
draught, and quickens the circulation of air through the 
vats. 

In another process, the weak alcoholic liquor trickles 
down through perforated casks, filled with beech shav- 
ings, which have been thoroughly scalded to remove all 
soluble matter. Air is admitted by holes around the 
lower part of the cask, and passes out at the top. 

When vinegar is purified, and concentrated by distil- 
lation, it constitutes the acetic acid of commerce. This 
is prepared on a large scale from pyroligneous acid, 
or wood vinegar (174), which is obtained by the de- 
structive distillation of wood. 

207. Bread-making. — The making of bread in the 
ordinary way, by means of leaven or yeast, is an example 
of alcoholic fermentation. 

When the grain of wheat is ground in a mill, and then 
sifted, it is separated into two parts, the bran and the 
flour. The bran is the outside harder part of the grain, 
which is not ground so readily, and, when ground, makes 
the flour darker. Both the bran and the flour consist 
mainly of gluten, starch, and "water. 

If the flour be mixed with water enough to moisten 
it thoroughly, the particles cohere and form a dough, 
which can be kneaded or moulded with the hand. It 
is the gluten of the flour which gives the tenacity to 
the dough. 

A little leaven or yeast is added to the flour, either 
before it is mixed with water into a dough or in the 



158 FERMENTATION. 

course of this process ; and the dough is then placed for 
some hours in a warm atmosphere, in order that it may 
rise. This rising is a fermentation, caused by the leaven 
or yeast. Leaven is the primitive ferment, and is simply 
a piece of moistened dough which has begun to putrefy. 
When brought in contact with a fresh portion of flour 
and water, it very quickly acts as a ferment, and develops 
fermentation in the whole mass. Yeast, as has been 
stated, is one of the vegetable growths which are fer- 
ments (200, 201). 

The leaven or yeast soon begins to act on the gluten, 
starch, and sugar of the flour, and a portion of the sugar 
is converted into carbonic acid and alcohol in every part 
of the dough. The bubbles of gas, thus disengaged in 
the mass, form innumerable cavities, and make it light 
and porous. 

The spongy dough is now put into a hot oven, where 
the fermentation and swelling are at first increased by the 
heat ; but when the whole has been heated to about 21 2°, 
the fermentation is suddenly arrested, and the mass be- 
comes fixed in the form it has then attained. In the bak- 
ing, some of the water is dissipated from the dough, the 
starch and gluten are partially boiled, and some of the 
starch is converted into dextrine. The brown, glossy 
appearance of the crust is due to this formation of dex- 
trine (162). Most of the alcohol is driven off by the 
heat ; but a large amount of water (about 45 per cent of 
the weight of the bread) remains in the loaf after the 
baking. 

There are various methods of making bread without 
fermentation, most of which depend on the liberation of 
carbonic acid from one of its compounds, by means of an 
acid. Bicarbonate of soda and muriatic acid are the ma- 
terials sometimes used. Cream of tartar, which is a 
compound of tartaric acid (165), is often used as the acid. 



FERMENTATION. 



*59 



The salt and acid are usually mixed with the dough, and 
the carbonic acid there set free ; but in the manufacture 
of the so-called aerated bread, water charged with the 
gas is used in making the dough, as in the English 
method,* or the gas itself is forced into the dough, as the 
process is conducted in this country. 



SUMMARY. 

Fermentation is the breaking up of complex organic 
compounds into simpler ones, by the agency of certain 
plants called femtents. 

The alcoholic fermentation takes place in sugar, and 
produces alcohol and carbonic acid. 

In making alcoholic liquors from grain, the starch 
of the grain is converted into sugar, by the action of 
diastase, as in the germination of seeds. The sugar is 
then converted into alcohol by the use of a ferment, as 
yeast. 

The alcohol of fermented liquors may be separated 
from the water, and concentrated by distillation. 

By the action of acids upon alcohol, important com- 
pounds called ethers are obtained. 

The acetous fermentation takes place in alcohol, which 
undergoes oxidation, producing vinegar, or acetic acid. 

The making of bread with yeast is an example of 
alcoholic fermentation. 

* See article on Aerated Bread in " Chambers's Encyclo- 
paedia;" also Fownes's "Chemistry," ioth edition (London, 
1868), page 605. 



APPENDIX. 



QUANTIVALENCE. 

The atoms of the different elements differ not only in their 
weight and the intensity of their affinity, but also in their com- 
bining capacity, or the number of their affinities. Thus an atom 
of chlorine is able to attach itself to only one atom of hydrogen : 
while an atom of oxygen can attach itself to two atoms of hydro- 
gen ; and an atom of carbon, to four atoms of hydrogen. The 
combining capacity of an atom is usually called its atomicity, or 
quantivalence. It may be represented graphically by means of 
dots and dashes : the latter being used when the affinity is 
exerted in holding together two atoms ; and the former, when it 
is not so employed. Thus H-O-H indicates that an atom of 
oxygen h?3 two affinities, and 'an atom of hydrogen one, and 
that these affinities are employed in holding the atoms of hydro- 
gen to that of oxygen. H* and •(>, on the other hand, indicate 
that the affinities of the two atoms are unemployed. 

As regards their atomicity, the elements have been found to 
fall into six classes : those whose atom has one unit of com- 
bining capacity, called univalents, or monads ; those whose atom 
has two units, called bivalents, or dyads ; those whose atom has 
three units, called trivalents, or triads; those Avhose atom has 
four units, called quadrivalents, or tetrads; those Avhose atom 
hasyzzx? units, called quinquivalents, ox pentads ; and those whose 
atom has six units, called sexivalents, or hexads. 

Those of ujieven equivalence are usually classed together as 
perissads ; and those of even equivalence, as artiads. 

In some cases, a part of the combining units of an atom often 
remain dormant, so that it seems to have two equivalences. 

ii 



i6z 



APPENDIX. 



TABLE. 

^^"The elements are grouped according to their quantiva- 
lence, which is designated by the Roman numerals. Those 
marked with a * are non-me*ats ; aii the others are metals. The 
names of the rarer elements are in italics. 



Perissad 
Elements. 



Hvdroaren 



Fluorine* 
Chlorine* 
Bromine* 
Iodine* 



Lithium 

Sodium 

Potassium 

Rubidium 

Ccesium 

Silver 



Thallium 



Gold 
Boron* 



Nitrogen* 
Phosphorus* 
Arsenic* 
Antimony* i 
Bismuth* 



Vanadium 



Uranium 



C aluminum 
Tantalum 



1.9 

<i 

~ l70 \ 
19.O 

35 5 

80.0 

127.0 

70 

230 

39-ij 

85.4! 

U3-o 

108 o 1 

204.0 

197.0J 

n. o 

l 
140 

31-oi 
75-oj 

I22.o| 
2IO O 

51-37! 

120.0 

940 

182.0 



H 
F 

CI 
Br 
I 
Li 

Na 
K 
Rb 
Cs 

Ag 

Tl 

An 

B 

N 

P 

As 

Sb 

Bi 

V 

U 

Cb 

Ta I 



O 



I or HI 
III 

III or V 



Artiad 

Elements. 

Copper 
Mercury 



Calcium 
Strontium 
Barium 
Lead 



Magnesium 
Zinc 



Indium 

Cadmium 



Glucinum 

Yttrium 

Erbium 



Cerium 

Lanthanum 

Didymium 



Artiad 
Elements. 



Oxygen* 



Sulphur* 
Selenium* 

Tellurium* 



Molybdenum 

Tungsten 



16.0 

32.0 s 

79.4' Se 

128.0 Te 

96 o ! Mo 
184.0 W 



II 
II or VI 



VI 



Nickel 

Cobalt 

Manganese 

Iron 

Aluminium 

Chromium 

Ruthenium 

Osmium 

Rhodium 

Iridium 



Palladium 
Platinum 



Titanium 
Tin 



Zirconium 



Thorium 



Silicon* 



Carbon* 



<n 


in 


E-S 


O 


J=> 




s 


<£ 


>> 

en 


63-4 


Cu 


200.0 
40.O 


Ca 


87.6 


Sr 


I370 


Ba 


207.O 


Pb 


24.O 


Mg 


65.2 


Zn 


72 O 


In 


1 12.0 


Cd 
G 


61.7 


y 


1 12.6 


E 


92 


Ce 


93-6 


La 


95° 


D 


S8.8 


Ni 


58.8 


Co 


55-o 


Mn 


56.0 


Fe 


274 


Al 


52.2 


Cr 


104.4 


Ru 


199.2 


Os 


i 104.4 


R 


196.0 
1 106.6 


Ir 
Pd 


197.4 


Pt 


50.0 


Ti 


1 18.0 


Sn 


89.6 


Zr 


231.4 


Th 


28.0 


Si 


12.0 


c 1 



& _ 

ir 



II or IV 



IV 



APPENDIX. 163 

When all the combining units of the atoms are employed, the 
molecule is said to be saturated ; otherwise, unsaturated. Thus 
H-Cl, H 2 =0, C§0 2 , and H 4 iN-Cl are saturated molecules, but 
:00, N=0 2 , :S=0 2 , are unsaturated molecules. These unsatu- 
rated molecules can enter directly into combination with other 
atoms or groups of atoms, while the saturated molecule* cannot 
Thus :00 can unite directly with an atom of oxygen, forming 
0=00, orCi0 2 ; but C§0 2 , cannot take any additional atom to 
itself, for the simple reason that there is no remaining point of 
attachment 

Such unsaturated molecules as the above are usually called 
compound radicals. When they enter into combination, they are 
supposed to exist in the molecule as a distinct group, or, as it 
were, a molecule within a molecule; just as Saturn with his 
group of rings and moons exists as a distinct system within our 
solar system. The compound radicals already given are known 
in the free state ; but there are many such groups, which are sup- 
posed to exist in compounds, but have never yet been obtained 
free. 

The equivalence of a radical is always equal to the number of 
its uncombined units. 

In some cases, the atoms of the same element often unite by 
a part of their affinities, and thus form elementary radicals. 
Thus in all the mercxwotis and cuprous compounds, we find the 
dyad radicals Hg 2 and Cu 2 , formed by the union of two atoms, 
•Hg-Hg', or Hg 9 : and 'Cu=Cu - , or Cu„:. Also in the ferr/c, man- 
gan/'c, chrom/c, and alumin/c compounds we have the sexivalent 
radicals Fe 2 , Mn 2 , Cr 2 , and Al 2 , formed thus : — 

iFe-Fe; or Fe 2 l , iMn-Mn- or Mn 2 i , etc. 

But, of all the elements, the atoms of the tetrad carbon mani- 
fest the greatest disposition to unite with one another by a part 
of their affinities, especially when their remaining affinities are 
satisfied by atoms of hydrogen. 

Thus two atoms of cai"bon may unite with each other by one, 
two, or three of their affinities, as shown by the following 
graphic formulas: — 

•C-C-, :C=C:, OC\ 



164 APPENDIX. 

Again, into each one of these radicals may be introduced one 
or more carbon atoms ; thus : — 



•C-C-, -C-C-C-, -C-C-C-C-, -C-C-C-C-C-, etc. 

II. 
MOLECULAR STRUCTURE. 

1. Types. By the locking together of multivalent atoms, as 
was illustrated in the case of carbon in the last section, it is seen 
that a great number of atoms may be introduced into a molecule. 
This number sometimes reaches several hundred. Yet all these 
molecules seem to be constructed after three or four simple pat- 
terns, or types ; the atoms of the simple typical molecule being, 
in the case of the more complex molecules, replaced by more or 
less complex radicals. 

The most important molecular types are those of hydrogen 
and of -water. 

The symbol of the first is H-H. By replacing one of the 
atoms of hydrogen in this molecule with an atom of each of 
the monad non-metals, we get (without change of molecular 
structure) the hydracids H-Cl, H-I, H-Br, and H-F. By re- 
placing the second atom of hydrogen in any one of these acids 
by an atom of any of the monad metals, we get (still without 
any change of molecular structure) such haloid* salts as Na-Cl, 
K-Br, Ag-I, etc. 

By replacing one atom of hydrogen in each of two mole- 
cules of any one of their acids by an atom of any of the dyad 
metals, we shall get (by a simple condensation of two molecules 
into one) the haloid salts of the dyad metals. Thus 

H-Cl S lves ^ a( ^Cl or Ca=Cl 2 

By a similar condensation carried to a greater degree, we may 
get the haloid salts of the metals and metallic radicals of higher 
equivalence. 

* Salts formed from the hydracids are often called haloid salts. 



APPENDIX. 165 

It will thus be seen, that the hydracids and the haloid salts all 
belong to the molecular type of hydrogen, with or without co?i- 
densation. 

The molecule of water may be written H-O-H, or H 2 =0. 

By replacing the first atom of hydrogen by an atom of a 
monad metal, we may get (without any change in molecular 
structure) such metallic hydrates as K-O-H, or KHO, and 
Na-O-H, or NaHO, etc. 

By replacing both atoms of hydrogen by atoms of the nomad 
metals, we may get (still without any change of structure) the 
metallic oxides K-O-K, or K 2 0, Na-O-Na, or Na 2 0, etc. 

By replacing one or both atoms of hydrogen by the univalent 
radical N0 2 , we may get H-0-N0 2 , or HNO s (nitric acid), or 
N0 2 -0-N0 2 , or N 2 5 (nitric anhydride), of precisely the same 
molecular structure as water. 

Again, we may replace one of the atoms of hydrogen by an 
atom of a monad metal, and the other by the univalent radical 
N0 2 . with no change of molecular structure, and thus get the 
salt K-0-N0 2 , orKN0 3 (potassic nitrate). 

By a simple condensation of one molecule of the water type, 
we get other salts of the monad and dyad metals. Thus : — 

h .q. h may give H >S0 2 ,or H 2 S0 4 ; 

H~0 >S ° 2 ' or KHS °4 5 K-0 >S ° 2 ' ° r K2SC>4 ; 
CaCg."^ or Ca(HO) 2 ; Ca<g;*J°a, or Ca(N0 3 ) 2 ; 

Ca<g>S0. 2 , or CaSO^ ; etc. 

In a similar manner, it may be shown that all the ternary 
acids and salts, and all the metallic hydrates and oxides, and a 
host of other compounds, belong to the water type, with or with- 
out condensation. 

[For further information on this point, see the " Elements of Chemistry " of the 
"Cambridge Course of Physics," pp. 79-843116! 345-352.] 

2. Substitution. — " When cotton-wool is dipped in strong 
nitric acid (rendered still more active by being mixed with twice 
its volume of concentrated sulphuric acid), and afterwards 



l66 APPENDIX. 

washed and dried, it is rendered highly explosive; and, although 
no important change has taken place in its outward aspect, it is 
found on analysis to have lost a certain amount of hydrogen, 
and to have gained from the nitric acid an equivalent amount of 
nitric peroxide, N0 2 , in its place." 

C 12 H 2) 1 { ) (cotton) becomes C 12 H 14 (NO 2 ) 6 O 10 (gun-cotton). 

Under the same conditions, glycerine undergoes a like change, 
and is converted into the explosive nitro-glycerine. 

G 6 H 10 O 6 (glycerine) becomes C 6 H 10 (NO 2 ) 6 O 6 (nitro-glycerine). 

So also the hydro-carbon, naphtha, called benzole, is changed 
into nitro-benzole. 

C G H 6 (benzole) becomes C 6 H 5 (N0 2 ) (nitro-benzole). 

" The last compound is not explosive, and the explosive nature 
of the fir&t two is. in a measure, an accidental quality, and is 
evidently owing to the fact, that into an already complex 
structure there have been. introduced, in place of the indivisible 
atoms of hydrogen, the atoms of a highly unstable radical, rich 
in oxygen. The point of chief interest for our chemical theory 
is, that this substitution does not alter, at least profoundly, the 
outward aspect of the original compound. Every one knows 
how closely gun-cotton resembles cotton-wool. In like man- 
ner, nitro-glycerine is an oily liquid, like glycerine; and nitro- 
benzole, although darker in color, is a highly aromatic, volatile 
fluid, like benzole itself. Products like these are called substitu- 
tion products; and they certainly suggest the idea that each 
chemical compound has a certain definite structure, which may 
be preserved even when the materials of which it is built are, in 
part, at least, changed. If, in the place of firm iron girders, we 
insert weak wooden beams, a building, while retaining all its 
outward aspects, may be rendered wholly insecure. And so the 
explosive nature of the products we have been considering is 
not at all incompatible with a close resemblance, in outward 
aspects and internal structure, to the compounds from which 
they are derived." 

3. Isomorphism. — "Closely associated with the facts of the 
last section, which find their chief manifestation in substances 



APPENDIX. 167 

of organic origin, are the phenomena of isomorphism, which are 
equally conspicuous among artificial salts and native minerals. 
There seems to be an intimate connection between chemical 
composition and crystalline form, and two substances which, 
under a like form, have an analogous composition, are said to be 
immorpkous" The following minerals are isomorphous : — 

Calcite, or calcic carbonate, CaC0 3 

Magnesite, or magnesic carbonate, MgC0 3 
Chalybdite, or ferrous carbonate, FeCO a 

Diallogite, or manganous carbonate, MnCO s 

" The most cursory examination of these symbols will show 
that they differ from each other only in the fact that one metal- 
lic atom has been replaced by another. It is not, however, every 
metallic atom which can thus be put in without altering the 
form. This is a peculiarity which is confined to certain groups 
of elements, which for this reason are called groups of isomor- 
phous elements. Moreover, as*a rule, there is a close resemblance 
between the members of any one of these groups in all their other 
chemical relations. These facts, like those of the last section, 
tend to show that the molecules of every substance have a deter- 
minate structure, which admits of a limited substitution of 
parts without undergoing essential change, but which is either 
destroyed or takes a new shape when, in place of one of its 
constituents, we force in an uncomformable element. A well- 
known class of artificial salts called the alums affords even a 
more striking illustration of the principles of isomorphism than 
the simpler examples we have chosen." 

4. Isomerism, Allotropism, and Polymorphism. — The same 
atoms may be grouped together in different ways, so as to form 
different molecules, which present essentially distinct qualities. 
Hence distinct substances may have the same composition; and 
they are then said to be isomeric, and the phenomenon is called 
isomerism. Thus, common sugar and gum arabic have exactly 
the same composition, C 12 H.220 n , and are isomeric. 

When, "however, the differences are not sufficiently great to 
justify a distinct name, the two bodies are said to be different 
allotropic states of the same substance, and the phenomenon is 



1 68 



APPENDIX. 



called allotropism. Thus, there are three varieties of tartaric 
acid which differ in their action on polarized light, but which 
are in almost every other respect identical. 

Sometimes a substance crystallizes in fundamentally different 
forms, as calcic carbonate in the minerals calcite and aragonite. 
This phenomenon is called polymorphism, and is invariably 
accompanied by a marked difference of properties. 



III. 



THE SPECTROSCOPE AND ITS APPLICATIONS 
IN CHEMISTRY. 

i. The Spectroscope. — This instrument (Figure 31 a) consists 
of a triangular piece of glass, P, called a prism, and three tubes, 

Fig. 31 a. 




A, B, and C. The tube A is an ordinary telescope. The tube 
B has a narrow slit in its outer end, through which a beam of 
light is admitted. This beam is concentrated by a lens upon 



APPZNDIX. IO9 

the prism P. The tube C has at its outer end a fine scale 
marked on glass. The light from the candle F shines through 
this glass, and is reflected by the face of the prism into the tele- 
scope A, so that on looking into this telescope an enlarged 
image of the scale is seen. The light from the tube B, on pass- 
ing through the prism, is dispersed into what is called a spectrum, 
which is examined by means of the telescope A. With ordinary- 
candle-light this spectrum is a continuous band of colored light, 
made up of the seven prismatic colors, red, orange, yellow, green, 
blue, indigo, and violet. 

This simple instrument was invented in 1859, D J two German 
professors, Bunsen and Kirchhoff, and it has already led to most 
remarkable discoveries in both Chemistry and Astronomy. 

2. Spectra of Incandescent Gases. — The spectrum of an ordi- 
nary candle or gas-flame is called a continuous spectrum. If, 
however, we dip a platinum wire into a solution of some sodic 
salt, and hold it in the colorless flame of a Bunsen's lamp, so as 
to color it with incandescent sodium vapor, we shall get a spec- 
trum, consisting of a single yellow line, as shown at III. in the 
chromolithic plate at the beginning of this book. Color the 
flame in a similar manner with incandescent potassium vapor, 
and we get a spectrum like II. in the plate, continuous in the 
middle, with a bright line at each end. The incandescent vapors 
of the rare metals ccesium and rubidium give spectra like IV. and 
V. in the plate. 

As a rule, the spectra of incandescent gases are broken, or 
discontinuous ; that is, made up of bright lines separated by 
dark spaces. The spectrum of each element is unlike that of 
every other element, either in the number or the position of its 
bright lines, and usually in both. 

The position of these lines can be ascertained with great accu- 
racy by means of the scale, which is seen in the telescope in the 
same position as the spectrum ; and for the same substance 
the position of the bright lines is always the same. 

3. Use of the Spectroscope in Chemical Analysis. — We have 
now seen that, as a rule, the spectra of incandescent gases are 
discontinuous, and that each is peculiar to itself. No matter 
how many gases there may be In the flame, each will give its 



170 APPENDIX. 

own lines, and no others. Hence we have in the spectroscope a 
valuable means of recognizing the elements which exist in a sub- 
stance of unknown composition. We have merely to heat its 
vapor to incandescence, examine it with the spectroscope, read 
off the position of the bright lines on the scale, and compare 
it with the position of the bright lines given by known ele- 
ments. 

This method of chemical analysis by spectrum observation 
is of wonderful delicacy. The .000000005 of a grain of a sodic 
compound can easily be detected in this way. Sodium is found 
to be always present in the air. All bodies that are exposed to 
the air show the yellow sodium line when heated. Of lithium 
.00000016 of a grain can be detected. This element was for- 
merly known to exist in only four minerals : it is now found by 
spectrum analysis to be one of the most widely distributed of 
elements. It exists in almost all rocks, in sea and river water, 
in the ashes of most plants, in milk, human blood, and muscular 
tissue. 

One of the first fruits of spectrum analysis was the discovery 
by Bunsen, in 1861, of the two new elements, ccesium and ru- 
bidium. They were found in the mineral waters of Durkheim ; 
forty-two tons of which had to be boiled down in order to obtain 
two hundred grains of the metals. 

It was by spectrum analysis also that thallium was discovered 
by Crookes, in 1861 ; and indium, by Reich and Richter, in 1864. 
The spectrum of the former metal consists of a splendid green 
line, and its name is derived from 6u/u6g (Latin, thallus), a 
green twig; that of the latter is made up of two indigo bands, 
whence the name indium. 

4. Use of the Spectroscope in the Bessemer Process. — Not only 
has the spectroscope proved valuable in the analysis of chemical 
compounds, and in the discovery of new elements, but it has 
also become of important service to the manufacturer of steel. 
In the "Bessemer process" (page 55), every thing depends 
upon shutting off the blast of air at just the right moment. If 
the blast be continued ten seconds beyond the right moment, 
the charge becomes too viscid to be poured from the converter ; 
if it be stopped ten seconds too soon, the steel contains so 



APPENDIX. I7l 

much carbon that it will crumble under the hammer like cast- 
iron. 

The flame undergoes various changes during the process, but 
only workmen of great skill and experience can tell by a simple 
inspection of the flame just when to shut off" the air. By the use 
of the spectroscope, however, any one can tell with the utmost 
exactness the proper moment to stop the blast. After showing 
a great number and variety of bright and dark bands, the spec- 
trum all at once becomes continuous, and experience has shown 
that this is the precise moment for shutting off the air. 

5. Use of the Spectroscope for detecting Adulterations, etc. — 
When light is allowed to pass through certain solutions, as that 
of potassic permanganate, or through certain coloring sub- 
stances, as madder, magenta, or chlorophyl, and is then exam- 
ined by the spectroscope, the spectrum is found to be crossed 
by dark bands, called absorptio7i bands. As each of these sub- 
stances gives absorption bands peculiar to itself, we have in 
these bands a ready means of recognizing the substance, and 
also of detecting adulterations in a medicinal compound or in a 
dye-stuff. The purity of wines may thus be tested, since the 
coloring-matter of the grape gives absorption bands wholly un- 
like those of the adulterations used. 

By means of the spectroscope, too, the .001 part of a grain of 
the coloring-matter in a bJood-stain can be detected with abso- 
lute certainty. Hence, the instrument has become a most 
valuable aid in medico-legal investigation. 

[For the applications of the Spectroscope in Astronomy, see the " Handbook of the 
Stars" or the " Elements of Astronomy," published in the " Cambridge Course of 
Physics."] 

IV. 

DISSOCIATION. 

1. Heat tends to overcome Cohesion and Affinity. — We have 
seen that sensible masses of matter are made up of insensible 
molecules, and these molecules of yet smaller masses called 
atoms. The atoms of a molecule are held together by affinity ; 
and the molecules, in solids and liquids, by a force called co~ 



172 APPENDIX. 

hcsion. //cat may partially or wholly overcome this cohesive 
force, and convert a solid into a liquid, and a liquid into a gas. 

We have further seen that heat will in some cases break up 
the molecules themselves, and thus decompose the compound, 
as in the preparation of oxygen from potassic chlorate. 

In 1857, tne celebrated French chemist, Henri St. Claire 
Deville, first called attention to the fact that any substance may 
be decomposed if sufficiently heated. This spontaneous decom- 
position of substances under the influence of heat he calls 
dissociation. He thinks that the dissociation of compounds, 
like the melting of solids or the boiling of liquids, takes place at 
a definite temperature, which is different for each substance. 
Thus nitric anhydride decomposes spontaneously at the ordinary 
temperature; amnionic carbonate dissociates at 6o° C, and am- 
monia gas at a red heat. He thinks that water is dissociated at 
a temperature of about 1000 C. 

In the case of water, and most other compounds, the fact of 
dissociation is not ordinarily observable, because on cooling 
down the atoms reunite so as to form the original compound 
again. Thus, if heated above 1000 C, the vapor of water is really 
separated into hydrogen and oxygen atoms, but on cooling down 
they again unite with each other so as to form water. 

It would at first seem that the theory that heat tends to over- 
come affinity, and to separate the atoms of a molecule as well as 
the molecules themselves, is at variance with certain well-known 
facts ; as the refusal of hydrogen and oxygen to enter into com- 
bination till heated. In this and many other cases heat seems 
to aid affinity rather than oppose it. A little consideration will, 
however, show that these cases do not necessarily conflict with 
the theory. We must remember that the molecules of hydrogen 
and oxygen, as well as the molecules of water, are made up of 
atoms, and that these atoms must separate or dissociate before 
they can enter into new combinations so as to form new 
molecules. An element may, according to our view, undergo 
dissociation as well as a compound. At a sufficiently high 
temperature, all molecules, whether elementary or compound, 
would be broken up, and all matter be resolved into atoms. 
The first effect of the heat then, in the above case, is to disso- 



APPENDIX. 173 

ciate the atoms in the molecules of hydrogen and oxygen ; but 
as the point of dissociation of these gases is below that of water, 
the atoms of hydrogen thus set free combine with those of 
oxygen and form water. At a still higher temperature the water 
is dissociated, but on cooling down the dissociated hydrogen 
atoms unite with those of oxygen before they are sufficiently 
cool to reunite with each other, so as to form ordinary hydrogen 
gas. 

If by any means the atoms of hydrogen could, after the dis- 
sociation of water, be separated from those of oxygen, we should 
in the end obtain ordinary hydrogen and oxygen gases. 

On the iSth of March, 1861, Deville published a series of 
researches* upon the influence exerted by certain porous vessels 
upon the composition of the gases that pass through them. A 
porous porcelain tube was placed in the interior of a larger glass 
tube, and each was provided with separate gas-escaping tubes. 
On causing hydrogen to pass through the interior tube, and 
carbonic acid gas through the outer space, the two gases were 
found to exchange places, and an inflammable gas collected at 
the end of the carbonic acid tube. It thus appeared that the 
hydrogen passed through the pores of the porcelain tube, and 
was replaced-by the carbonic acid. 

The previous experiment with hydrogen and carbonic acid was 
repeated with steam and carbonic acid. In a furnace capable of 
producing a heat of 1100 to 1300 C. he placed two tubes; 
through the interior tube of porous clay he forced a gentle cur- 
rent of steam, and through the annular space of the outer tube 
a stream of carbonic acid gas. A part of the vapor of water 
is decomposed spontaneously, or dissociated, in the tube of 
porous clay; the hydrogen is filtered through to the annular 
space (as in the previous experiment with carbonic acid and 
pure hydrogen), and the oxygen remains in the inner tube, 
mixed with a considerable quantity of carbonic acid. Deville 
obtained in this way one cubic centimetre of gas to one gramme 
of water. The separation of the oxygen is thus accomplished 
by physical agency. 

* This account of Deville's experiments is condensed from an article written by 
Professor Charles A. Joy, of Columbia College, New York. 



1 74 APPENDIX. 

It will thus be seen that Deville was able to dissociate the 
oxygen and hydrogen of water, and to obtain these gases in a 
separate condition. His experiment suggests a method for the 
accomplishment of this desirable result in an economical man- 
ner. By employing the carbonic acid resulting from the fire 
used to generate the steam, we can conceive of a simple system 
of tubes that would enable us to dissociate water in a way that 
would yield hydrogen and oxygen for light and heat. 

Deville published an account of another series of experiments, 
February 13, 1865. He conducted these upon a somewhat dif- 
ferent plan. He had early observed that, although compounds 
were dissociated at high temperatures, yet, on cooling, the ele- 
ments recombined before they could be collected ; it therefore 
became necessary for him to devise some plan to obviate .this 
difficulty. He hit upon the following expedient: Through the 
centre of the system of tubes he arranged a tube for conducting 
a constant stream of cold water. While the outer vessel was 
raised to the highest temperature of the furnace the inside 
was cold, and thus two surfaces were exposed to the gas, one for 
dissociating it, the other for condensing one of the constituents 
before it could recombine. In this way he succeeded in dis- 
sociating sulphurous acid at 1200 C. into sulphur and sulphuric 
anhydride; muriatic acid into hydrogen and chlorine; carbonic 
oxide into carbon and carbonic acid; and carbonic acid into 
carbonic oxide and oxygen. 

2. The Chemical Action of Light. — Several compounds are 
decomposed under the influence of light. This is especially the 
case with the salts of silver. When these salts are in contact 
with organic matter and exposed to the light, they blacken more 
or less rapidly. This blackening is due to a decomposition 
effected by the light. Some of the silver is set free in a very 
finely divided state, and thus appears black. The chemical 
action of light is quite analogous to that of heat. In this and 
other cases it acts against affinity, and tends to break up the 
molecules of a compound. 

In the case of hydrogen and chlorine, it appears to aid affinity; 
for if we place a mixture of these two gases in direct sunshine, 
they unite with a violent explosion, while in the dark they will 



APPENDIX, 



*75 



remain mixed any length of time without combination. But 
here also the direct action of the light undoubtedly tends to 
separate the atoms from each other in the molecules of hydrogen 
and chlorine, so that they may combine anew to form! muriatic 
acid- The strong disposition of the hydrogen and chlorine 
atoms to combine doubtless aids the light. 

As a rule, the more refrangible the rays, the stronger their 
chemical action; but different substances are affected by rays 
of different refrangibility. Tyndalfs recent experiments with 
vapors indicate that the decomposition is effected by the partic- 
ular rays which the body absorbs. 



V. 
PHOTOGRAPHY. 

i. The Camera. — If a lens be placed at an opening in a shut- 
ter of a darkened room, and a screen be placed at a proper dis- 
tance behind it, a beautiful inverted image of the objects outside 
the window will appear on the screen. The arrangement just 
described is called a camera obscura, and photography is the art 
of fixing the image of the camera permanently to the surface 
upon which it falls. This is done by the chemical action of light. 

The form of camera used by photographers is shown in Figure 
31 b. The lenses for forming the image are in the tube A, and 

Fig. 31 b. 




I7& APPENDIX. 

the screen for receiving it is a piece of ground glass, E. This 
screen is capable of a backward and forward movement, and is 
adjusted so that the image upon it is perfectly clear and distinct. 
The glass plate is then removed, and a surface sensitive to the 
action of light is put in its place. 

The various photographic processes may be considered under 
three heads : photography on metal, photography on paper, and 
photography on glass. 

2. Photographs on Metal. — It was in the year 1839 that the 
problem of taking pictures by light was first successfully solved 
by a Frenchman named Daguerre. 

The Daguerreotype picture is taken on a plate of copper coated 
with silver. The plate is first carefully polished, and then ren- 
dered sensitive by exposing its silvered surface to the vapor of 
iodine, which forms upon it a thin layer of argentic iodide. If 
the picture is to be taken quickly, the surface must be made still 
more sensitive by the action of bromine. All these operations 
must be performed in a room lighted by a candle. The plate is 
now put into a little wooden case, and exposed in the camera. 
After a little time, it is removed to a darkened room. No change 
perceptible to the eye has taken place. But when the plate is 
exposed to the vapor of mercury, an image appears exactly like 
that formed in the camera. The mercury condenses upon those 
parts of the plate that have been most strongly illumined, and 
thus develops the picture which before was latent. The action 
of the light gives the molecules of the argentic iodide a tendency , 
to decompose, and the tendency of the mercury to unite with 
the silver completes the decomposition of these molecules. In 
the shades of the picture, the molecules of the iodide have ac- 
quired no tendency to break up, and those parts are not attacked 
by the mercury. 

If, after the development of the picture, the plate were exposed 
to the light, the iodide on all parts of the surface not attacked 
bj-tbe mercury would gradually blacken, and the picture become 
obliterated. In order to fix the picture, it is necessary to dis- 
solve and remove this iodide, which is usually done by a solu- 
tion of sodic hyposulphite. 

The picture is next toned hy immersing the plate in a solution 



APPENDIX. Ifrtf 

of auric chloride. Some of the gold unites with the mercurv 
and silver of the parts attacked, and greatiy increases the inten- 
sity of the lustre. 

The lights of the Daguerreotype picture consist of the amal- 
gam ; and the shades, of metallic silver. 

3. Photographs on Paper. — Photographs on paper are 01-di- 
n&rily printed from negatives on glass. 

If gun-cotton be put into a mixture of alcohol and ether, it 
dissolves and forms collodion. If this solution is poureu over 
any surface, the alcohol and ether quickly evaporate, leaving a 
film of solid collodion behind. 

To obtain a sensitive surface on glass, a solution of collodion 
is first impregnated with potassic iodide, or a mixture of potassie 
iodide and amnionic bromide, and poured out upon the surfacft 
of a glass plate, so as to coat it with a thin film. The plate 
thus coated is dipped into a bath of argentic nitrate, so as ta 
form a film of argentic iodide, or a mixture of argentic iodide 
and bromide. The plate is now exposed a short time in the 
camera, and again removed to a darkened room. As before, no 
image is perceptible. The light has not decomposed the com- 
pounds of silver, but merely given them a disposition to de- 
compose. Their decomposition is completed, and the picture 
developed, by pouring over the plate a solution of ferrous sul- 
phate or of pyrogallic acid. The picture is next fixed by dissolv- 
ing off the argentic iodide from the unaffected part by means of 
the solution of sodic hyposulphite. 

The glass is rendered less transparent by the presence of the 
metallic silver: hence, when viewed by transmitted light, the 
lights of the image appear dark; and the shades, light; and the 
picture is therefore said to be a negative. From this negative 
picture any number of positive pictures may be printed on paper. 
For this purpose, paper is impregnated with argentic chloride, 
by dipping it first into a solution of common salt (sodic 
chloride), and then into a bath of argentic nitrate. The nega- 
tive is then placed on a sheet of this paper in a copying-frame, 
and exposed to the action of light. The chloi-ide gradually 
blackens, and most rapidly where the glass is most transparent. 
In this way the tints of the negative are reversed, and the picture 

12 



IJ& APPENDIX. 

becomes a positive. After sufficient exposure, the nicturs is 
fixed by dissolving off the remaining chloride by a solution of 
sodic hyposulphite, and toned by immersing it in a bath of auric 
chloride. 

4. Photographs 071 Glass. — The picture on glass, which ap- 
pears negative by transmitted light, will become positive if it be 
backed with a coating of black varnish or a piece of black cloth, 
so that it shall be seen by reflected light. 

Beautiful positive pictures on glass may be obtained by the 
following process : prepare the plate in the same way as for 
negatives, but expose it a much shorter time in the camera; 
develop the picture by pouring over it a solution of ferrous sul- 
phate, which gives a negative image; then pour a solution of 
potassic cyanide over the plate, and this negative is rapidly 
converted into a positive. 



VI. 

THE CHEMISTRY OF LUMINOUS FLAMES. 

Until a very recent day, all scientific men laid it down as a 
rule without exceptions, that the light of flames is due to solid 
oodies or solid particles intensely heated. Frankland, in 1S67, 
was the first to dispute this theory, and to show that there may 
be very bright flames in which no solid particles are present. 
He burned a jet of hj'drogen in a tube filled with oxygen, and, 
gradually increasing the pressure upon the gas to twenty atmos- 
pheres, he found the brilliancy of the flame to increase with the 
pressure. At a pressure of ten atmospheres, a burning jet of 
hydrogen an inch in length gave ligh^ enough for reading a 
newspaper at a distance of two feet from the flame. He also 
found that carbonic oxide, which usually burns with a very pale 
name, burned very brightly under great pressure. In the first 
case, the product of the combustion was water, which must 
ftjive existed in a gaseous state in the flame : in the second case, 
Eiie Dtouuct was carbonic anhvdr/de, which must also have bee?i 
a sras. In both cases, the gas in the flame was rendered more 
dense by the pressure. 



APPENDIX. 279 

If arsenic be burned in a stream of oxygen gas, it yields a 
dazzling white •flame, though neither the arsenic nor the prod- 
uct of its combination with oxygen can remain solid at the 
temperature of the flame. The same is true of sulphur and 
phosphorus when burned in oxygen. The latter burns with a 
brightness that is almost blinding, and yet the phosphoric 
anhydride which is produced is so readily volatilized that it can 
hardly exist as a solid, even at the extreme outer surface of the 
flame. 

These facts, and many others of the same sort, prove that the 
luminosity of flame may sometimes be due, not to the presenc? 
of solid particles, but to that of dense gases or vapors, intensely 
heated. Frankland's experiments appear to show that, as a rule, 
the denser the vapor the brighter will be the flame. If the 
pressure of the air upon a flame is increased, it becomes more 
luminous; if the pressure is diminished, it becomes less lumi- 
nous. The flame of a common spirit-lamp grows bright in 
condensed air; and a candle gives more light at the foot of a 
mountain than at its top, though the rate of combustion is nearly 
the same in both cases. 

Are we to explain the light of an ordinary candle or gas flame 
in this way? Frankland believes that we should do so. Hydro- 
gen, as we know, has a far greater attraction for oxygen than 
carbon has ; consequently, when both are present, and the supply 
of oxygen limited, the hydrogen takes up the greater portion of 
the oxygen to the exclusion of a great part of the carbon. Now, 
this happens, in the case under consideration, at some little 
distance within the outer surface of the flame, that is, in the 
luminous portion ; the little oxygen which has penetrated thus 
far inward is mostly consumed by the hydrogen, and hydro- 
carbons are separated, rich in carbon and of great density in the 
state of vapor. These hydrocarbons, which would form smoke 
if they were cooler, and are deposited as soot* on a cold body 
held in the flame become intensely ignited by the burning 
hydrogen, and evolve a light whose whiteness marks a very 

* Frankland has shown that soot is not pure carbon, but a mixture of heavy hydro- 
carbons. 



l8o APPENDIX. 

elevated temperature. In the exterior and scarcely visible part 
of the flame, these hydrocarbons undergo combustion. 

If the gas be previously mixed with air (as in the Bunsen's 
lamp), or if air be forced into the interior of the flame, the hydro- 
gen and carbon burn together, forming vapors much less dense, 
and the luminosity almost disappears. 

Such, in brief, is Frankland's explanation of the phenomena 
of ordinary illumination, and the teacher can use it in whatever 
way he pleases, in connection with the corresponding portions 
of §§ 192-194, 197, and 199. The new theory appears to be quite 
generally adopted by scientific men ; but no one ought to be 
ignorant of the old one, which will continue to have at least a 
historic interest from the fact that it was so long universally 
accepted as a complete explanation of all the varied phenomena 
of luminous flames. 

It is proper to add that Frankland does not presume to assert 
that the decomposition of hydrocarbons in the gas-flame is 
never complete, — in other words, that particles of elementary 
carbon are never separated, — but he is fully satisfied that "the 
incandescence of solid particles is not the chief condition of 
luminosity," but that the light is " mainly due to the ignition 
of dense hydrocarbon vapors." 

Certain obvious facts connected with gas-flames are perfectly 
consistent with this new theory, while they are not easily ex- 
plained under the old one. The flame from a common fish-tail 
burner is so transparent that the smallest print can be read 
through any part of it without the least difficulty. We find, 
too, that the edge of such a flame gives just as much light as 
its flat side does. If the light proceeded from solid particles, 
the most luminous part of the flame ought to be more or less 
opaque ; and, as such particles would obstruct the light of those 
behind them, the edge of the flame ought to be less bright than 
the side. 

On the whole, we must admit that some of the phenomena 
of luminous flames can be satisfactorily explained only by 
Frankland's theory, and that probably it furnishes the correct 
explanation of nearly all such phenomena. 



APPENDIX. 



181 



VII. 



EXERCISES AND PROBLEMS. 

As it is of the greatest importance that the scholar should be- 
come, at the start, thoroughly acquainted with the chemical 
nomenclature and notation, we give below various exercises for 
practice. We would advise that considerable time be spent upon 
these before the pupil is allowed to go further with the text. 



Table 


I. 


Na 2 is 


sodi 


c oxide. 


Na 2 S „ 


>> 


sulphide 


Na 2 S0 4 „ 


>> 


sulphate 


NaCl „ 


•>■) 


chloride. 


NaNO s „ 


>> 


nitrate. 


NaHO „ 


5> 


hydrate. 





Table I] 


. 


BaO 


is 


baric oxide. 


BaS 


aj 


,, 


sulphide. 


BaS0 4 


?» 


>j 


sulphate. 


BaCl 2 


?> 


,, 


chloride. 


Ba(N0 3 ) 2 * 


»> 


?> 


nitrate. 


Ba(HO) 2 


'■) 


»? 


hydrate. 



Al 2 O s 

A1 2 S 3 

Al 2 (SC> 4 ) 3 , 
A1 2 C1 6 , 

Al 2 (N0 3 ) 6 , 
Al 2 (HO) 6 , 



Table III. 
is aluminic oxide. 



sulphide. 

sulphate. 

chloride. 

nitrate. 

hydrate. 



How many and what elements in sodic oxide? 

In baric chloride? In aluminic nitrate? 

In sodic hydrate? In baric sulphate? 

"What element in every compound in the above tables whose 
name ends in -ate P 

Does a binary compound ever have this ending to its name? 

In what does the name of a binary compound always end? 

What element does the ending -ate indicate? 

Does every compound containing this element have this end- 
ing to its name? 

* A figure placed thus after parentheses multiplies all the atoms enclosed therein. 
Thus (NOj) 2 indicates 2 atoms of N and 6 of O. 



lh>2 APPENDIX. 

How many and what atoms in a molecule of sodic chloride? 
In sodic sulphide? In aluminic chloride? In baric sulphate? 
In sodic nitrate? In sodic sulphate? In baric nitrate? 
In aluminic hydrate? In sodic hydrate? In aluminic sulphate? 

Each of the compounds in the above tables may be regarded 
as made up of two parts; namely, a metal combined with a 
single atom or group of atoms. Thus, Na 2 is made up of the 
metal Na and the non-metal O ; Na 2 S0 4 , of the metal Na and 
the group of atoms S0 4 . The metal may be called \hejirst part 
of a compound; and the atom or group of atoms with which it 
is combined, the second part. 

What group of atoms in every sulphate? 

In every hydrate? In every nitrate? 

How many atoms of the metal in a molecule of each of the 
first three compounds of Table I.? 

Of the last three compounds of Table I.? 

Of each of the compounds of Table II.? of Table III.? 

How many of the second part in a molecule of each of the first 
three compounds of Table II.? Of the last three of Table II.? 

Of the first three of Table III. ? Of the last three of Table III. ? 

Of each of the compounds of Table I.? 

H, K, Ag, and Am (ammonium, H 4 N) form compounds like 
Na. What, then, is the symbol for potassic oxide? 

For argentic sulphide ? Argentic chloride ? Potassic sulphate ? 
For potassic hydrate? Argentic nitrate? Hydric oxide? 
For hydric sulphide? Hydric chloride? Hydric sulphate? 
For hydric nitrate? Amnionic hydrate ? Ammonic nitrate? 
For amnionic chloride? Ammonic oxide? Ammonic sulphate? 

For what elements do Sr, Ca, Zn, Pb, Cu, Hg, and Mg 
respectively stand? 

Each of these elements forms a series of compounds exactly 
like those of Ba. What, then, is the symbol for strontic oxide? 

For zincic sulphide? Calcic nitrate? Plumbic sulphate? 

For mercuric chloride? Cupric sulphate? Calcic hj-drate? 

For magnesic oxide? Zincic nitrate? Calcic sulphate? 

For plumbic sulphide? Cupric oxide? Mercuric nitrate? 



APPENDIX. I S3 

For what elements do the symbols Fe, Mn, and Cr stand? 

Each of these elements forms two series of compounds : one 
like those of Ba ; and the other like those of Al. The names of 
the former end in -ous ; and those of the latter, in -ic. 

What is the symbol for ferrous oxide? 

For manganic oxide? Ferric sulphide? Chromic nitrate? 

Formanganous sulphate? Ferric chloride? Manganic chloride? 

For chromous oxide? Ferric sulphate? Ferric nitrate? 

For ferrous sulphate? Ferric oxide? Ferrous nitrate? 

For manganous oxide? Chromic oxide? 

The symbols for the iodides, bromides, and fluorides are writ- 
ten just like those of the chlorides. 

What is the symbol for argentic iodide? 

For potassic bromide ? Calcic fluoride ? Ferric iodide ? 

For ferrous bromide? Ammonic bromide? Hydric iodide? 

The symbols of the carbonates are written just like those of the 
sulphates, the last part being C0 3 , instead of S0 4 . 

What is the symbol for sodic carbonate? 

For ferric carbonate? Calcic carbonate? Potassic carbonate? 

For ammonic carbonate? Plumbic carbonate? Magnesic 
carbonate? 

Correct the following symbols, and give the name of the 
compound after correction : — 

K 2 C1, AgO, Ba 2 S, Pbl, A1C1 3 , NaS0 4 , Agl 2 , K 2 N0 3 , Ca 2 CO s , 
Ca. 3 (N0 3 ) 2 , A1 2 S0 4 , KC0 3 , Ag 2 N0 3 , A1 2 O g , A1S 3 , Zn a O, CuCl, 
Fe 2 0, Fe0 3 , Fe 2 S0 4 , Fe (S0 4 ) 3 , FeNO, SrBr, HgCl, Pb 2 S0 4 . 

What elements form compounds like Na? Like Ba? Like Al- 

Almost every chemical change is called a rcactio?i, but the 
most common reactions are the changes which take place when 
the solutions of two substances are mixed. Thus, if we mix 
hydric sulphate with baric nitrate, the hydrogen and barium 
change places, and we get baric sulphate and hydric nitrate. 

Such reactions can be expressed by equations ; thus : — 
H 2 S0 4 + Ba(N0 3 ) 2 = BaS0 4 + H 2 (N0 3 ) 2 , or 2HNO3. 

The reaction maybe read and explained thus : hydric sulphate 
and baric nitrate give baric sulphate and hydric nitrate, the 
hydrogen and the barium changing places. 



184 APPENDIX. 

Read and explain the following reactions : — 

BaCl 2 + CuS0 4 = CuCl 2 + BaS0 4 . 

Sr (N0 3 ) 2 + Am 2 C0 3 = Am 2 (NO s ) 2 , or 2 AmN0 3 + SrC0 3 . 

Pb (N0 3 ) 2 + 2KI, or K 2 I 2 = K 2 (N0 3 ) 2 , or 2 KN0 3 + Pbl 2 . 

What symbols are wrong in the following reaction ? 

Pb (NO a ) 2 + KI = K (N0 3 ) 2 + Pbl. 

How many atoms of K and I are needed in the second member 
of the equation? How many, then, must there be in the first? 
Correct the following reaction, and explain the correction : — 

CuS0 4 + KHO = KS0 4 + CuHO. 

A?is. This should be 

CuS0 4 + 2KHO, or K 2 (HO) 2 = K 2 S0 4 + Cu (HO) 2 . 

There must be 2 molecules of KHO, because there must be two 
atoms of K in the potassic sulphate, and 2 (HO) in the cupric 
hydrate formed in the reaction. 

Correct the following, with explanation : — 

ZnS0 4 +KHO = KS0 4 +ZnHO. 

Fe (NO :3 ) 2 + AmHO = Am (N0 3 ) 2 + FeHO. 

H 2 S + AgN0 3 = AgS + H 2 N0 3 . 

Al 2 (S0 4 ) 3 + 3AmHO, or Am 3 (HO) 3 = 

Am 3 (S0 4 ) 3 , or 3AmS0 4 + Al 2 (HO) 3 . 

AgN0 3 -f 2KI, or K 2 T 2 = K 2 N0 3 + Agl 2 . 

Write out and explain the reaction between manganous sul- 
phate and sodic hydrate. 

Between manganous sulphate and amnionic carbonate. 

Baric chloride and amnionic carbonate. 

Calcic nitrate and ammonic carbonate. 

Hydric chloride and plumbic nitrate. 

Hydric sulphide and plumbic nitrate. 

Cupric sulphate and potassic iodide. 

Argentic nitrate and hydric sulphate. 

[The teacher can easily multiply these exercises, if he wants more of them.] 



NOTES ON EXPERIMENTS, 



APPARATUS. 

The following list includes all the apparatus needed for the 
more important experiments in this book : — 

i. Pneumatic trough. — Gases which are not absorbed by 
water, or but slightly so, can be collected bj first filling the 
vessel with water, and inverting it with its mouth under water. 
The tube through which the gas is escaping is introduced under 
the mouth of the jar, and the gas rises and fills the jar. 

For collecting gases in this way, a pneumatic trough is useful 
and almost indispensable. This apparatus consists of a vessel 
deep enough to allow of filling and inverting under the water 
any of the jars ordinarily used. A shelf perforated with holes 
extends across the vessel about an inch under the surface of the 
water. After the jar is filled with water and inverted, it is set 
upon the shelf over one of the holes. The delivery tube (which, 
except the part passing through the cork, may be of rubber) is 
then passed into this hole, and the jar filled. It is convenient 
to have a shelf large enough to hold several jars, after they have 
been filled with gas. 

The best pneumatic trough is made of soapstone or copper; 
but any vessel which will hold water and has a perforated shelf 
will answer the purpose. The teacher can easily provide him- 
self with such a trough ,at little expense. 

2. Two glass cylinders : one, i inch in diameter and 5 inches 
deep; the other, i^ inches in diameter and 7 inches deep. These 
should have ground mouths and be provided with ground-glass 
plates for covers. 



l86 APPENDIX. 

3. Two two-quart glass jars, with ground mouths and ground 
plates for covers. 

4. Two nipper-taps. A nipper-tap is a convenient substi- 

Fig, 32 tute for a stop-cock. 

^__ By means of it a 

/^r^^^^^^X ^Ew^ rubber tube can be 

nu ^S---^sx0^Wl pinched close. The 

II ^ jSgi.^ ll === ^ = _ best kind is shown 

\\ - ;__ /jf^ ^S^r^^ ^-^i^^ (full size) in Figure 

^^^^l^^^^^^ ^ La':,:'^" 32. The tube is com- 
..-""" - pressed by a spring. 

5. One two-gallon india-rubber gas-bag. This may be closed 
with a rubber cork, through which passes a short glass tube, 
connected with a second glass tube by a short piece of rubber 
tubing, which may be closed with a nipper-tap. Such an ar- 
rangement is cheaper than a stop-cock, and better, since gases 
sometimes corrode the latter. 

6. A bottle generator. This consists of a wide-mouthed pint 
bottle, closed with a rubber cork, through which pass two tubes; 
one, large and straight, and passing nearly to the bottom; the 
other, small, and bent at right angles, passing only through the 
cork. An ordinary cork will answer, but rubber corks are 
always to be preferred for chemical apparatus. They cost more 
at first, but they last much longer, and make perfectly tight 
joints. 

7. Three half-pint flasks. One, at least, of these should have 
a rubber cork through which passes a bent delivery-tube. 

8. An iron lamp-stand with three rings. 

9. A lamp. A Bunsen's lamp is much to be preferred where 
gas is to be had; otherwise, an alcohol lamp. 

10. A wooden retort-holder with two clamps. 

11. A hydrogen generator. The most convenient apparatus 
for preparing hj^drogen is the self-regulatmg generator shown 
in Figure 33. It consists of a glass vessel closed with a metallic 
cap. A bell-shaped glass vessel, open at top and bottom, is fast- 
ened to this cap by an air-tight joint. A tube closed by a stop- 
cock passes through the cap into the bell-shaped vessel. A 
copper bucket perforated with fine holes is hung from a hook 



APPENDIX. 



l8.7 




inside this vessel. This bucket is filled with Fig- 33- 

shreds of sheet zinc or bits of granulated zinc. 

The outer vessel is filled about two-thirds full 

of dilute sulphuric acid (the ordinary oil of 

vitriol diluted with about ten parts of water). 

The metallic cap with the bell-glass attached 

is then put in its place, and the stop-cock 

opened. The air is first driven out, and the 

dilute acid coming in contact with the zinc 

begins to act upon it, and hydrogen is given 

off in abundance. When sufficient hydrogen 

has been obtained, the stop-cock is closed, the 

hydrogen generated collects in the upper part 

of the bell-glass, and drives the acid out. As soon as the acid 

is driven out, the action ceases until the stop-cock is opened 

again, and the hydrogen allowed to escape. By means of rubber 

tubing, the hydrogen can be conveyed from the generator to the 

jar or vessel in which it is to be collected. When hydrogen 

is to be burned, the greatest care must be taken that all the air 

is driven out of the apparatus before the gas is collected. 

12. A chlorine tube. This is a glass-tube, 1 of an inch in 
diameter, and 15 inches long, closed at one end. The other end 
should be provided with a rubber cork, through which passes a 
glass tube drawn out to a fine jet inside. This should be con- 
nected with a small glass funnel by means of a short piece of 
rubber tubing, which may be closed by a nipper-tap. 

13. Two small beakers. 

14. Two evaporating dishes. 

15. A U-tube (Figure 5). One end of the tube should be 
closed, and near this closed end two platinum wires should 
pass through the sides so as nearly to meet within. These 
wires should terminate outside in loops. It is not necessary 
that the U-tube should be tubulated at the bend, as represented 
in the figure, or fastened to a stand, since it may be held in the 
clamp of the retort-holder. 

16. A chalk cup. This is a cylinder of chalk, about 12 inches 
in diameter and 2 inches high, hollowed out at the top. 

17. Awash-bottle. This is like No. 6. The rubber tube which 



1 88 APPENDIX. 

is delivering the gas should be connected with a glass tube small 
enough to pass down through the straight glass tube to the 
bottom. 

18. A nitric-oxide bell and jar. The bell is half the capacity 
of the jar, and the mouths of both are ground, so as to fit to- 
gether air-tight. 

19. An asbestos tube. 

20. A half-pint tubulated retort. 

21. A dozen 5-inch test-tubes. 

22. Haifa pound of glass tubing, 5 of an inch in diameter. 

23. 4 feet of rubber tubing, 3 of an inch in diameter. 

The following additional apparatus will be needed for experi- 
ments with the oxy-hydrogen blowpipe : — 

Two 25-gallon gas-bags, with stop-cocks and tubing. 

An oxy-hydrogen jet. 

A copper flask for making oxygen. 

EXPERIMENTS. 

1. (§ 1, Exp. 1.) Use bottle generator (No. 6 in list of appa- 
ratus above). The end of the long tube must be k j pt beneath 
the surface of the acid. The acid is diluted with 2 or 3 parts of 
water. The hydrogen may be collected in the small glass cylin- 
der (No. 2) ; but the gas which first comes off must not be col- 
lected, as it is mixed with air, and therefore explosive. 

2. (§ 1, Exp. 2.) Use flask (No. 7) with rubber cork. Pour 
in strong muriatic acid first, so that none of the dry manganese 
may stick to the flask. Use only a small quantity of the mate- 
rials, as the chlorine is very disagreeable if it escapes into the 
room. It is well to have a large jar filled with water, ready to 
receive any chlorine that may come off after the small cylinder 
has been filled. It will be well also to let the gas which first 
comes off pass into this jar until the air is expelled from the 
flask. The flask should be supported on the ring of the lamp- 
stand (No. 8), and should be separated from the flame, either by 
a sand-bath or, better, by a piece of fine wire gauze. 

3. (§ 1, Exp. 3.) Use the smaller glass cylinder (No. 2). 
Let the hydrogen pass in first until it is half full, and then fill 



APPENDIX. 



189 



the remainder with chlorine. Close the cylinder under water 
with the glass plate, bring it near the lamp, remove the glass 
plate, and quickly put the mouth of the cylinder into the flame. 
The explosion is not very violent with these small quantities. 
Never attempt to use large quantities, and be careful to keep tl.e 
mixed gases out of direct sunshine. 

Another way of per- pj g 34 

forming the experiment 
is to use two cylinders of 
the smaller size (No. 2), 
filling one with hydrogen 
and the other with chlo- 
rine. Cover them with the 
glass plates, and place 
them together, mouth to 
mouth, as represented in 
Figure 34. Then with- 
draw the glass plates, 
keeping the mouths of 
the cylinders together, 
shake the cylinders to mix the gases, and open them over a 
burning lamp, as shown in Figure 35. 

4. (§ 2, Exp. 1.) The Fig. 35- 
sodium used must be pure, 
else there is danger of an 
explosion. The smaller 
cylinder (No. 2) must be 
used and held in the 
clamp of the retort-holder 
(No. 10). The sodium 
may be first thrown upon 
the water, and then thrust 
under the cylinder by means of a perforated metallic cup, which 
may be made out of a-thimble by punching a few holes through 
the top, and fastening a wire round it for a handle. 

5. (§ 2, Exp. 2.) The water may be saturated with chlorine 
by putting it in a wash-bottle (No. 17), and allowing the chlo- 
rine to pass through it as long as it is taken up by the water. 





XCJO APPENDIX. 

The delivery-tube of the bottle should be connected with a jar 
over the water-trough, in order that no chlorine may escape into 
the room. The chlorine water thus prepared may be put in the 
larger cylinder (No. 2), inverted in a soup-plate of water, and 
set in the sunshine. 

6. (§ 2, Exp. 3.) Fill one of the jars (No. 3) with oxygen, 
and let it stand over the trough long enough to drain. Burn the 
hydrogen as it escapes from the generator (No. 11) through a 
glass tube bent at right angles and drawn out to a fine jet; and 
hold the jar of oxygen over the flame. 

Glass tubing may be bent by heating it red-hot in the flame 
of the lamp. A tube may be drawn out to a fine jet by heating 
the middle red-hot, and then quickly pulling the ends apart. It 
may be cut by scratching it a little on one side with a three- 
cornei-ed file, and then bending it over the thumb-nails, held 
close together on the side opposite the scratch. 

7. (§ 3, Exp. 1.) Fill chlorine tube (No. 12) with chlorine 
over the water-trough. Close the mouth while under water with 
the thumb, invert it, and insert the cork. Pour a little strong 
ammonia into the funnel, and let it drop slowly into the tube by 
means of the nipper-tap, to the depth of half an inch. Close 
the nipper-tap, and pour off the ammonia from the funnel ; and 
then fill the funnel with water, and let it run into the tube, care 
being taken to keep water in the funnel all the time, so that no 
air may get into the tube. 

In this and all other cases where chlorine is to be used, it will 
be best to prepare it beforehand, and keep it in a gas-bag till 
wanted. On its way from the generating flask to the gas-bag, 
it should be passed through a wash-bottle containing a small 
amount of water. The gas is washed to remove any muriatic 
acid which may be in it, and v/hich would corrode the bag. 

S. (§ 6, Exp. 1.) Fill the bent tube in the first place with 
water, close it with the thumb, and invert it over water. Then 
allow a little hydrogen to« pass into it from the generator, and 
also some oxygen from a gas-bag which has been previously 
filled with this gas. With a little care, one can readily get the 
right proportions. The tube should not be more than two- 
thirds full of the mixed gases, and a considerable excess of one 



APPENDIX. I9I 

gas should be used, so that enough may be left for testing. 
After putting the gases into the tube, close it with the thumb, 
raise it from the water, and tip it so that the gases may pass into 
the closed arm; then pour out a little of the water, and again 
close it with the thumb. Connect the outer coating of a charged 
Leyden jar with one of the platinum loops, by means of a wire 
or chain, and bring the knob of the jar in contact with the other 
loop. After the spark has passed, again fill the open arm with 
water, close it with the thumb, and tip the tube so as to transfer 
the remaining gas to the open arm, and there test it. 

9. (§ 10, Exp. 1.) As explosions sometimes occur in the 
manufacture of oxygen, care should be taken that the chemicals 
are pure; and it would be well to test each purchase by putting 
some of the potassic chlorate in an iron spoon and heating it 
over a spirit lamp until it is melted; then stir into it with an 
iron wire some of the black oxide of manganese; and if these 
materials are not good, an explosion will take place, and a 
whitish mass with red spots in it will be left in the spoon. If, 
however, the chemicals are pure, there will be no explosion, and 
the melted mixture will soon dry up, leaving a dark gray re- 
siduum. If the bubbles come over too violently, remove the 
lamp for a few minutes until they come more moderately. 

A glass flask may be used ; but as it is liable to break, a cop- 
per flask may perhaps be found cheaper in the long run, espe- 
cially if one has to make oxygen often. 

10. (§ 11, Exp. 1.) Use glass jar (No. 3). The charcoal may 
be fastened to a piece of wire and ignited in the flame of a lamp. 
It is well to have the other end of the wire attached to a copper 
or wooden disk, which serves to cover the jar while the charcoal 
is burning. 

Lime-water may be made by putting a small quantity of 
slaked lime into a jar (No. 3) of water, stirring it thoroughly, 
and allowing it to settle. The clear liquid may then be poured 
off into a bottle, and kept for use. 

n. (§ 11, Exp. 2.) Fill a jar (No. 3) with oxygen, and let it 
stand to drain. Put a piece of sulphur in the chalk cup (No. 
16), ignite it by touching it with a red-hot wire, and invert a 
jar of oxygen quickly over it. The jar should be kept closed 



192 APPENDIX. 

with the plate until it is inverted, and brought just over the sul- 
phur. The chalk cup should stand in a shallow dish of water, 
so that the mouth of the jar may dip under the water and pre- 
vent the S0 2 from escaping into the room. 

12. (§ 11, Exp. 3.) The phosphorus may be burnt in the 
same way as the sulphur. As phosphorus is a very inflammable 
substance, and as burns from it are very slow to heal, great 
caution must be exercised in using it. The sticks must always 
be cut under water, and it must be carefully dried, by pressing 
it between pieces of unsized paper, before it is burnt; else it will 
fly about in a very disagreeable and dangerous manner. It 
should always be lighted by touching it with a heated wire, 
never by holding it in the flame of a lamp. 

13. (•§ 11, Exp. 4.) The watch-spring should be either 
straightened out or formed into a spiral, and fastened to a disk 
of copper or wood, as above described. Water should be left in 
the bottom of the jar to the depth of two inches or so, that the 
melted globules of iron may not burn into the jar. 

14. (§ 12, Exp. 1.) Ozone may be most easily prepared by 
pouring a little ether into a jar (No. 3), and then when the air 
in the jar has become saturated with the vapor of ether, stirring 
the air with a glass rod heated nearly to redness. 

15. (§ 20, Exp. 1.) In making hydrogen, use the hydrogen 
generator (No. 11). 

16. (§21, Exp. 1.) Mix the gases in the gas-bag, letting each 
gas pass in separately. The quantities can be estimated nearly 
enough by the eye. Fasten an ordinary clay tobacco-pipe to 
the gas-bag, hold the mouth of the pipe in soap-suds, and 
press out the mixed gases in a gentle stream. For obvious 
reasons, the nipper-tap should be closed before the bubbles 
are lighted. 

17. (§ 28, Exp. 1.) Fill the bottle generator (No. 6) one- 
third full with strong ammonia, and connect the large tube with 
a rubber bag filled with chlorine. Connect the delivery-tube 
with the wash-bottle (No. 17), and the delivery-tube of the wash- 
bottle with the larger cylinder (No. 2). Force the chlorine 
through the apparatus by compressing the bag. Care must be 
taken not to force an excess of chlorine through the ammonia, 



APPENDIX. 



93 



lest the very explosive nitric chloride (page 28) be foiTned. 
There is little danger, however, if slrong ammonia is used. 

18. (§ 30, Exp. 1.) Use the bottle generator (No- 6). First 
pour in water enough to cover the bits of copper (brass or nickel 
will do as well), and then pour in gradually strong nitric acid. 
The gas is very poisonous, and should not be allowed to escape 
into the room. 

19. (§ 30, Exp. 2.) The management of the experiment is the 
same as in the burning of phosphorus in oxygen (12). 

20. (§ 30, Exp. 3.) The gases may be mixed in a gas-bag. 
It is not necessary that the proportions should be exact. 

21 ' (§ 33i Exp, 1.) Use nitric-oxide bell and jar (No. 18). 



Fig. 36- 




Fill the bell with oxygen, and the jar with nitric 
oxide. The jar should be closed with a plate and 
set on the table, and the bell of oxygen set on the 
plate covering the jar (Figure 36). When the ex- 
periment is to be tried, the plate should be drawn 
out, and the mouths of the bell and jar allowed 
to come together. 

22. (§ 36, Exp. 1.) Use tubulated retort (No. 
20). Only a small quantity of the amnionic nitrate 
need be used. The retort must not be heated too 
much, lest the gas should come off with explosive 
violence. 

23. (§ 37, Exp. 1.) Gases, like ammonia and muriatic acid, 
which are absorbed by water, must be collected over mer- 
cury. 

For the experiments of this book we think a mercury-trough 
a needless luxury. An evaporating dish of Berlin porcelain 
answers every purpose. One five inches in diameter is large 
enough to use with the cylinders mentioned above. It should 
be set in a shallow dish of strong glass or earthen ware, to pre- 
vent loss of mercury in case of accident. It should then be 
filled nearly full of mercury. The cylinder to be used is next 
filled with mercury to the brim. The ground-glass cover is then 
placed on the mouth of the cylinder and held firmly with the 
right hand, thecjdinder inverted, and its mouth plunged beneath 
the mercury in the evaporating dish. It is well to put the cylin- 



i 9 4 



APPENDIX. 



der in a strong dish when you are filling and inverting it, to 
save any mercury which may be spilled. After the cylinder is 
filled and inverted over the mercury in the dish, the plate is 
slipped from its mouth, and the cylinder is securely fastened in 
the clamp of a retort-stand, so that its mouth is held about ^ or 
| of an inch above the bottom of the dish. 

To fill the cylinder with ammonia gas, a little aqua ammonia 
is put into a flask provided with a delivery-tube, and gently 
boiled. To the delivery-tube is attached apiece of rubber tub- 
ing to connect it with the cylinder. A short piece of glass tub- 
ing with its end slightly turned up must be fastened to the end 
of the rubber tube, so that the gas may be introduced into the 
cylinder through the mercury. On first boiling the aqua am- 
monia, a large amount of air passes over from the flask. The 
ammonia gas must not be collected until this has all passed 
over. To determine when this has taken place, put the glass 
tube at the end of the rubber tube into a vessel of water; when 
heat is first applied to the flask, bubbles of gas will rise from 
the end of the tube through the water as long as any air comes 
over. When the air is all over, the ammonia gas is absorbed 
by the water as fast as it comes over, and no bubbles rise to the 
surface. After the air ceases to come over, plunge the end of 
the glass tube into the mercury, and introduce it under the 
mouth of the cylinder. The gas will rise into the jar and dis- 
place the mercury. 

When the cylinder is rilled with 
ammonia, close it with a glass 
plate, and remove it to a vessel of 
water; then open the mouth of 
the jar under the water (Fig- 
ure 37). 

24. (§ 43, Exp. 1.) The oxalic 
acid may be heated with sulphuric 
acid in a flask, and the solution 
of soda put in a wash-bottle. 

25. (§ 45, Exp. 1.) In both ex- 
periments, the sulphur should be 
heated cautiously, that it may not 



Fig- 37- 




APPENDIX. I95 

take fire. Figure 38 shows the needle- p. g 

shaped crystals which may be obtained 
by the first experiment. 

26. (§ 53, Exp. 1.) With the aid of 
an air-pump, phosphorus may be burnt 
in chlorine in the following manner : 
Place the chalk cup, with a bit of phos- 
phorus in it, on the bottom of the nitric- 
oxide jar (No. 18), and cover the jar -=-r 
with a well-fitting glass plate which has 




in its centre a round hole, 1 of an inch in diameter. This hole is 
closed with a rubber cork, through which passes a glass tube 
connected with a second glass tube by a short piece of rubber 
tubing provided with a nipper-tap. Connect the jar with the 
air-pump by rubber tubing, and exhaust the air. Close the 
nipper-tap, and connect the jar with a gas-bag filled with chlo- 
rine. Open the nipper-taps, and let the chlorine pass into the 
jar, until the pressure within is nearly but not quite equal to that 
outside. The phosphorus will soon take fire. If the jar were 
filled full of chlorine, the heat of the burning phosphorus would 
expand the chlorine, and force out some of it into the air. 

27. (§ 60.) The color of iodine vapor may be shown by heat- 
ing a few grains of iodine in a flask over the lamp. 

28. (§ 65, Exp. 1.) Use tubulated retort (No. 20). Fill it 
nearly full of water, put in a small piece of phosphorus, and let 
the mouth of the retort dip under water. Heat the retort until 
the water in it boils, and then drop in a stick of caustic potash 
through the tubulature. The water is boiled first in order to 
drive out the air from the retort, so that the hydric phosphide 
may not take fire inside, and thus cause an explosion. 

29. (§ 123, Exp. 1.) The process is the same as in the experi- 
ment in § ^^ using air instead of oxygen. 

30. (§ 123, Exp. 2 ) Observe the precautions given in § 12. 

31. (§ 142, Exp. 1.) ' The sugar and the potassic chlorate 
should be pulverized separately, and then mixed carefully. Put 
the mixture on an earthen dish, and let one drop of sulphuric 
acid fall upon it from the end of a long glass rod. The ex- 
periment is brilliant, even with much smaller quantities. 



QUESTIONS FOR REVIEW AND 

EXAMINATION. 



The numbers refer io tlie sections of the book. 

The Non-Metallic Elements. — i. Describe the experi- 
ments with muriatic acid. What products are obtained? The 
test for each? How may they be united again? 2. Describe 
the experiments with sodium and chlorine water. What are 
obtained? How is the oxygen tested? If hydrogen be burnt 
in oxygen, what is the product? What does this show? 3. De- 
scribe the experiment with ammonia. What new gas is ob- 
tained, and how is it tested? What does ammonia contain? 
4. Define compounds and elements. Give examples of each. 
How many elements? 5. What two classes of elements? What 
are symbols? What is the symbol of gold? of iron? Explain. 
6. What is affinity? What are its three characteristics? Illus- 
trate each. 7. What are molecules? atoms? Why so called? 
What is said of the atoms of an element? What of the mole- 
cules of a compound? What is this theory called? What is the 
atomic constitution of muriatic acid? of water? of ammonia? 
8. What symbols do compounds have? What is indicated by 
these symbols? Illustrate. 9. What are atomic weights? The 
atomic weight of H? of O? of N? of CI? How is the relative 
weight of the elements in a compound shown by the symbol? 
10. Describe the preparation of O from KC10 3 . What is a re- 
action? Express this reaction by an equation, and explain in 
full. 11. Describe experiments with charcoal, sulphur, and 
phosphorus. What product in each case? How may Fe be 
burnt in O? What product? What properties of O do these 
experiments illustrate? 12. What is ozone? Why so called? 



I98 QUESTIONS FOR REVIEW AND EXAMINATION. 

How obtained? How tested? 13. What are allotropic states? 
14. What are oxides? How named? 15. What are acid 
oxides? anhydrides? acids? Illustrate. Explain the names 
and symbols of acids. 16. What are basic oxides? bases? 
How named? Illustrate. What are alkalies? 17. What are 
neutral oxides? 18. What is a salt? How named? Illustrate-. 
19. What are binary compounds? ternary compounds? 20. 
How is H prepared? Express the reaction in an equation, and 
explain it. 21. What are the properties of H? Illustrate by 
experiments. 22. Describe the oxy-hydrogen blowpipe, and the 
experiments with it. What is the lime light? 23. The proper- 
ties of H 2 0? What is said of its solvent power? 24. What is 
said of rain water? spring water? mineral waters? hard and soft 
water? sea water? 25. What is said of H 2 in plants and 
animals? 26. What is water of crystallization? Efflorescence? 
Deliquescence? 27. Give some account of the uses of H 2 0. 28. 
How is N prepared? 29. The chief characteristic of N? 30. 
How is NO prepared? What experiments with it? 31. Define 
catalysis. 32. What is meant by the nascent state? ^. What 
is N 2 3 ? How prepared? 34. What is N0 2 ? N 2 G 5 ? HNO s ? 
35. The properties of HNO s ? How made? Illustrate by an 
equation. Explain the action of HN0 3 on metals? 36. What 
is N 2 0? How made? Its properties and uses? 37. What 
is H 3 N? When absorbed by water, what does it form? How is 
it prepared ? 38. What is ammonium ? Why is it considered a 
metal? 39. What is CN? How obtained? For what remark- 
able? What are some of its compounds? What are radicals? 
40. What are the characteristics of N? Illustrate each. 41. De- 
scribe the allotropic forms of C. 42. What is C0 2 ? Its prop- 
erties? How prepared? Explain. How tested? 43. What is 
CO ? Its preparation ? Properties ? 44. What are the sources 
of S? How is it purified? 45. Describe the allotropic forms of 
S. Its properties ? 46. What is S0 2 ? Properties and uses? Il- 
lustrate by experiment. 47. What is H 2 S0 4 ? Ways of making 
it? Explain in full. 48. What is S0 3 ? Properties? 49. What 
is H 2 S? Preparation? Properties and uses? 50. What is CS 2 ? 
How made? Properties? 51. What elements belong to the O 
group? Why thus classed? 52. How is CI prepared? Explain 



QUESTIONS FOR REVIEW AND EXAMINATION. 1 99 

the reaction. 53. Properties of CI ? Explain its bleaching 
power. 54. Describe the old and new methods of bleaching. 
How is bleaching powder made? For what else is it used? 
55. How is muriatic acid made? Explain the reaction. 56. 
What are hydracids? oxyacids? 57. What is aqua regia? Why 
so called? Explain its action on gold. 58. Give the names and 
symbols of the CI oxyacids. 59. Give the history and proper- 
ties of Br. 60. Where is I found? Its properties? 61. Proper- 
ties of F? How prepared? 62. What is HF? How made? 
Uses? 63. What elements in the CI group? What is said of 
them ? 64. Give the history and the sources of P. Its proper- 
ties? Uses? 65. What is said of the compounds of P? 66. 
What is said of As ? 67. What elements in the N group? Why 
thus grouped? 68. How is boracic acid obtained? For what 
is B remarkable? 69. What is Si0 2 ? What is said of Si? 
70. What is said of the C group? 

The Metals. — 71. What are some of the heaviest metals? 
some of the lightest? What is said of the melting-points of the 
metals? 72. What are ores? veins, or lodes? 73. What is Fe? 
Explain the symbol. What three forms of Fe in commerce? 
How is Fe made fibrous? How does it sometimes lose this tex- 
ture? Explain welding. 74. Describe the blast-furnace. How 
is cast-iron made? How converted into wrought iron? De- 
scribe the reverberatory furnace. 75. How is steel made? Its 
properties? Describe the Bessemer process. 76. What isPb? 
How obtained? Properties? What is the action of H 2 on 
Pb ? What is said of lead pipes lined with tin? How are lead 
pipes best protected from water action? 77. What are the chief 
ores of Cu? Properties of Cu? 78 What are some of the 
alloys of Cu ? Their composition ? For what are they remark- 
able? 79. What is Sn0 2 ? Where found? How is Sn obtained 
from it? Properties of Sn? Uses? What is said of tin water 
pipes? 80. What alloys of Sn are mentioned? 81. Chief ores 
ofZn? How reduced? Properties and uses of Zn ? Its alloys? 
82. Give the names and symbols of the iron oxides. What is 
FeS0 4 , and how is it made? Its uses? What other salts of Fe 
are mentioned? 83. The names and symbols of the lead oxides? 
What is PbC0 3 ? How is it made? Explain. What is the 



200 QUESTIONS FOR REVIEW AND EXAMINATION. 

chemical name and symbol of chrome yellow? 84. What are the 
oxides of Cu? What are the chief cupric salts? 85. What oxide 
of Zn? What salt is mentioned? 86. What is SnO? Sn0 2 ? 
What is a mordant? What salts of Sn are used as mordants? 
87. The chief ore of Hg? How reduced? Properties of Hg? 
Uses? What are amalgams? Describe the silvering of mir- 
rors. 88. Sources of Ag? Explain cupellation and amalgama- 
tion. Properties of Ag? What is said of the compound of Ag 
and S? 89. Where is Au found? How is it obtained? Prop- 
erties? 90. Whei-e and in what state is Pt found? How is it 
obtained from the ore? Its properties and uses? 91. Give the 
names and symbols of the oxides of Hg. What is calomel? 
corrosive sublimate? vermilion? 92. What two silver oxides? 
Their symbols? What is AgN0 3 ? AgCl? What silver salts 
are used in photography? For what is AgCN used? 93. What 
is Au 2 0? Au 2 3 ? What salts of gold are mentioned ? Their 
uses? 94. What is PtO ? PtC> 2 ? PtCl 4 ? 95. How was Na dis- 
covered? How obtained now? Properties? What is said of 
its compounds? 96. Where is Mg found? How obtained? 
Properties and uses? 97. The sources and preparation of Al? 
Its properties? 98. What is Sb? Its chief ore? How reduced? 
Properties? Alloys? 99. State the sources, properties, and uses 
of Bi. How is it now classed? 100. Name the properties and 
usesofNi. 101. Whatis Na 2 0? Na 2 2 ? HNaO? Its properties 
and uses? How made? State the reaction. 102. Give the 
chemical name and symbol of common salt. How is salt ob- 
tained from sea water? How are salt lakes formed? What is 
said of rock-salt? of salt springs? 103. What is Na 2 C0 3 ? Its 
uses? How was it formerly made? Give the history of the 
modern method? Describe the process in full. 104. How is 
HNaC0 3 made? Its commercial name? Uses? 105. What is 
the chemical name and symbol of soda-saltpetre? Its uses? 
What is Na 2 S0 4 ? Mention other sodic salts. 106. What is 
MgO? Epsom salts? 107. What oxide has Al? Its souixes 
and uses? What is alum-cake? Give an account of the alums. 
What is clay? kaolin? 108. Whatis glass? Describe the four 
kinds. Give an account of glass-making. What is porcelain, 
and how is it made? 109. What two oxides of Sb? Its chief 



QUESTIONS FOR REVIEW AND EXAMINATION. 20~ 

salt? no. What are the Bi oxides? What is Bi3NO s ? in. 
What two oxides of Ni? 112. How was K discovered? How is 
it now prepared? Its properties? What is pearlash, and how 
is it made? What are the chief potassic compounds? What is 
said of gunpowder? of KClOg? 113. Where does Ca occur? 
How is the metal obtained? What is CaO? Its preparation, 
properties, and uses? What is mortar? hydraulic cement? 
What is said of CaCO s ? of CaS0 4 ? of CaCl 2 ? 114. Give an 
account of Sr and its compounds. 115. What is said of Ba and 
its compounds? 116. The chief compounds of Cr and their 
uses? 117. Describe Co. What compounds are mentioned? 
118. Give an account of Mn. What oxides has it? Which is 
the most important? Its uses? 119-122. What is said of Cd? 
of Ir? of W? of U? 

Chemistry of the Atmosphere. — 123. Prove that the air 
contains free O. What are its other constituents ? Is it a com- 
pound of these gases? 124. What are the products of the burn- 
ing of a candle? Prove this. 125. Prove that the candle takes 
O from the air. 126. What is all ordinary combustion ? 127. 
Why is a draft needed in a stove? 128. What is a combustible? 
A supporter of combustion? What is true of these terms? Il- 
lustrate by an experiment. 129. What is necessary to make O 
unite with a combustible? 130. Show that combustion is self- 
sustaining. 131. Show that the point of ignition is different for 
different bodies. 132. When are products of burning gaseous, 
and when solid? 133. What is true of Mg? Give other exam- 
ples of the kind. 134. Show that O is not the only supporter of 
combustion. 135. What is true of the earth's crust? 136. Show 
that the materials of the earth are the results of burning. 137. 
What three states of O ? What is said of the third ? 138. What 
is decay? Describe the process, and explain in full. 139. Ex- 
plain the causes of decay. 140. What is rusting? Show that it 
develops heat. 141. Define and illustrate spontaneous combus- 
tion. 142. What is said of decay in animals? What three kinds 
of food? What does milk contain? What does bread? What 
purpose does each kind of food serve in the body? How is the 
body heated? Describe and explain in full. 143. What experi- 
ment illustrates the burning of sugar? 144. Give facts concern- 



202 QUESTIONS FOR REVIEW AND EXAMINATION. 

ing the daily consumption of O. 145. Describe the formation 
of the embryo plant in the seed. 146. Give an account of the 
growth and structure of the plantlet. 147. What are organic 
beings? What is organic structure? 148. Explain how plants 
get their food. 149. Of what does the inorganic portion of the 
plant consist? Why are manures necessary in agriculture? 
Why are fields allowed to lie fallow? Explain the principle of 
the alternation of crops. 150. Give an account of the organic 
portion of the plant. 151-153. How does the plant get H and 
O? C? N? 154. Show that the growth of plants is a chemical 
process, and how it is carried on. 155. Show that plants purify 
the air for animals to breathe. 156. Show that plants prepare 
food for animals. 157. What is said of the relations of plants 
and animals? 158. Give a full account of starch. 159. What is 
sugar? What two kinds? 160. What is the symbol for cane- 
sugar? From what is it obtained? Describe its manufacture 
from the cane, and the refining process. Give some facts, in the 
history of sugar. 161. What names has C 12 H 2i 12 ? In what is 
it found? How may it be made? Its uses? 162. What are the 
sources and uses of dextrine? 163. What is the symbol of cel- 
lulose? How is gun-cotton made? What is said of it? What 
is collodion? Its uses? 164. Describe the manufacture of 
vegetable parchment. Its uses? 165. What is said of C 4 H G O ? 
of its compounds? What is C 6 H 8 7 ? C 4 H 6 5 ? C 2 3 ? H 2 C 2 4 ? 
Give an account of tannic acid and tannin. 166. What is the 
composition of fats and oils? What two classes of oils? Give 
some account of both. 167. What is soap? How do hard and 
soft soap differ? The composition and uses of glycerine? 168. 
What is said of wax? 169. How do gums and resins differ? 
Mention the chief examples of each. 170. Give some account of 
vegetable alkaloids. 171. Describe the proteine bodies? Why 
are they important? 

Destructive Distillation and its Products. — 172. 
What is destructive distillation? 173. Describe the preparation 
of charcoal. 174. What are the products of the distillation of 
wood? 175. Describe wood naphtha. 176. What is creosote? 
Its uses? 177. Give an account of paraffine. 178. What is as- 
phalt, and for what is it used? 179. What is slow destructive 



QUESTIONS FOR REVIEW AND EXAMINATION. 20^ 

distillation? 180. Explain the formation of mineral coal. 181. 
What two kinds of coal? How do they differ? 182. How do the 
products of the distillation of soft coal and of wood differ? 183. 
What is found in coal-tar? What are the uses of carbolic acid? 
Of aniline and its compounds? i8|.-i86. What is said of benzole 
and nitro-benzole? of toluole and cumole? of naphthaline? 
187. Give the history of the coal-oil manufacture. 188. Explain 
the probable origin of petroleum. 189. How is petroleum ob- 
tained? 190. Give the history of coal-gas. 191. What is flame? 
192. What are the two conditions of illumination? 193. Ex- 
plain the burning of coal-gas. 194. Describe and explain 
Bunsen's lamp. 195. What is the best shape for a gas-flame? 
196. Describe the Argand burner. 197. Explain the Bude 
light. 198. Show that a burning candle is a miniature gas- 
factory. 199. Analyze the candle-flame. 

Fermentation. — 200. State the nature and causes of fer- 
mentation. Explain apparent cases of fermentation without a 
ferment. What two kinds of fermentation? 201. Explain 
the alcoholic fermentation. How is it brought about in grain? 
202. Explain the formation of diastase in plants. 203. Describe 
in full the process of brewing. 204. Describe the distilling and 
rectifying of spirits. 205. What is ether? Its properties and 
uses? Name other ethers. 206. Explain the acetous fermenta- 
tion. Describe methods of making vinegar. 207. Describe and 
explain bread-making. How may bread be made without fer- 
mentation? 



INDEX. 



For concise statements of the leading topics of the book, see the*6uMMARiES, 
which will be readily found by means of the Table of Contents. The references in this 
Index are only to the fuller treatment of subjects in the body of the work. 



A. 



Acid, acetic, 156. 

boracic, 44. 

carbolic, 138. 

carbonic, n, 29. 

chromic, 87. 

citric, 127. 

hydrochloric (see muriatic). 

hydrocyanic, 27. 

hydrofluoric, 41. 

hydrosulphuric, 35. 

hypophosphorous, 43. 

maLc, 127. 

muriatic, 3, 9, 38, 77. 

nitr.c, 24. 

nitrous, 24, 33. 

Nordhausen, 33. 

oxalic, 127. 

pho phor.c, 11, 13, 23, 43. 

picr.c, 138. 

prus ic, 27. 

pyroligneous. 134, 157. 

sulphur.c, 13, 33. 

sulphurous, 11, 13, 32. 

tannic, 127. 

tartaric, 126, 168. 

tungstic, 89. 
Acids, 13, 165. 

fatty, 128. 

vegetable, 126. 
Affinity, 8. 

characteristics of, 8. 
Alabaster, 86. 
Albumen, 131. 
Albuminous substances, 101, 103, 

no, 131. 
Alcohol, 155. 
Alkalies, 14. 

Allcalo ds, vegetable, 130. 
Allotropic states, 13, 166. 
Allotropism, 166. 
Alternation of crops, 114. 
Alum cake, 79 
Alumina, 79. 
Aluminium, 72, 98. 

salts, 79. 



Alums, 79, 167. 
Amalgamation, 66. 
Amalgams, 65. 
Ammonic chloride, 26. 
Ammonia, 6, 9, 23, 44, 115. 

preparation of, 26. 

produced by decay, 102. 
Ammonium, 26. 
Anaesthetics, 25, 156. 
Anhydride, carbonic, 11, 29, 91. 

nitric, 24, 91. 

nitrous, 24, 33. 

phosphoric, n, 13, 23. 

sulphuric, 13, 34 

sulphurous, 11, 13, 32. 
Anhydrides, 13. 
Aniline, 138. 
Animal heat, 104. 
Animals, food of, 131. 
Antimony, 72. 

salts, 82. 
Apparatus, list of, 185. 
Aqua ammonia, 23. 
regia, 39, 67. 
Argand burner, 147. 
Argentic salts, 69. 
Arrowroot, 121. 
Arsenic, 43. 
Asphalt, 136. 

Atmosphere, composition of, 91. 
Atoms, 9, 161. • 
Atomicity, 161. 
Auric salts, 70. 

B. 

Balsams, 130. 

Barilla, 76. 
Barium, 87. 

salts, 87. 
Bases, 14, 165. 
Bell metal, 58. 
Benzole, 13S. *39, i°6- 
Bessemer process, 55, 170. 
Bismuth, 73. 

salts, 82. 
Bleaching, 37. 

powder, 37. 



206 



INDEX. 



Blende, 60. 

Blowpipe, the oxy-hydrogen, 16. 

Boracic ac.d, 44. 

Borax, 44, 79. 

Boron, 44. 

Brass, 58. 

Bread, composition of, 103. 

making of, 157. 
Brewing, 154. 
Br.mstone, 31. 
Britannia metal, 60. 
Brom des, 40 
Bromine, 40. 
Bronze, 58. 

aluminium, 72. 
Bade light, the, 147. 
Bunsen's lamp, 146. 
Butter, 103. 

c. 

Cadmium, 89. 
Calamine, 60. 
Calcic carbonate, 85. 
chloride, 86. 
sulphate, 86. 
Calcium, 84. 

burns in air, 98. 
Calomel, 69. 
Candle, a gas- factory, 148. 

products of burning, 92. 
Candle -flame, analyzed, 148. 
Cane-sugar, 122. 
Caoutchouc, 130. 
Caramel, 123. 
Carbolic acid, 138. 
Carbon, 28. 

and oxygen, 146. 
Carbonic acid, n, 29, 91, 105, 115, 117. 

bisulphide, 35. 

group, 45. 

oxide, 30. 
Caseine, 103, 131. 
Catalysis, 23. 
Cellular structure, 109. 
Cellulose, 114, 125. 
Chalk, 84, 85. 
Charcoal, 11, 133. 
Chlorides, metallic, 181. 
Chlorine, 4, 36, 41. 

group, 41. 

nascent state of, 39. 

oxyacids, 39. 

preparation of, 36, 188, 19c. 

supports combustion, 98. 
Chrome yellow, 63, 88. 
Chromium, 87. 

salts, 87. 
Cinnabar, 64, 69. 
Clay, 80. 
Coal, 136. 
Coal-gas, 142. 
Coal-oils, 138. 
Coal-tar, 137. 
Cobalt, 88. 

compounds, 88. 
Coffee, alkaloid in, 130. 
tannin in, 128. 



Collodion, 126. 

Combustibles, 94. 

Combustion, nature of ordinary, 94. 

self-sustaining, 96. 

spontaneous 102. 

supporters of, 94. 
r^t^unds, 6 

binary, 15. 

molecules of, 9. 

ternary, 15. 
Copper, 57. 

alloys of, 58. 
salts, 63. 
Com-starch, 121. 
Corros.ve sublimate, 69. 
Cream of tartar, 127. 
Creosote, 135. 
Crops, alternation of, 114. 
Crystals, 167. 
Cumole, 139. 
Cupellation, 66. 
Cupric salts, 63. 
Cyanogen, 27. 

D. 

Decay, a slow combustion, 100. 

causes of, 10 1. 
Deliquescence, 19. 
Dextrine, 120, 125, 136. 
Diamond, the, 28. 
Diastase, 152. 
Dissociation, 171. 
Distillation destructive, 133. 

„ of coal, 137. 

„ ,, wood, 134. 

,, slow, 136. 

of spirits, 155. 
Draft in stoves and furnaces, 94. 
Drummond light, the, 16. 

E. 

Earth, the crust of the, 98, 99 
Earthen-ware, 80. 
Efflorescence, 19. 
Elements, 7. 

classification of the, 161. 

tables of, 7, 162. 
Epsom salts, 79. 
Ether, 155- 
Eupion, 135. 



Farina, 121. 
Fats, 128. _ 
Fermentation, acetous, 156. 

alcoholic, 152. 

causes of, 151. 
Ferments, 152. 
Ferric chloride, 61. 
sulphate, 61. 
Ferrous acetate, 61. 

sulphate, 61. 
Fibrine, 131. 
Flame, nature of, 145. 178. 



INDEX. 



207 



Fluorine, 41. 
Fluoi sprj-, 41, 
Food, 103. 

of animals, 13.T 

„ plants, in. 
Furnace, the blast, 52. 

the reverberatory. /, 

G. 

Galena, 56, 63. 

Garnet, 80. 

Gases, collection of, 185. 

» >, over mercury, ig3. 
Gelatine, 127. 
German silver, 61, 73. 
Glass, 80. 

soluble, 79. 
Gluten, 103. 

Glycerine, 128, i2g, 166. 
Glycose, 124. 
Gold, 67. 

salts, 70. 
Grape-sugar, 124. 
Graph. te, 28. 

Growth of plants, 108, 152; 
Gum-resins, 130. 
Gums, 129. 
Gun-cotton, 125, 166. 
Gunpowder, 84. 
Gutta-percha, 130. 
Gypsum, 84, 86. 

H. 

Heart, description of the. 104. 
Heat, animal, 104. 

produced by decay, 101. 
„ „ rusting, 102. 

Hydracids ? 39. 
Hydrates, 14. 
Hydraulic cement, 85. 
Hydric chloride (hydrochloric acid), 38. 
fluoride (hydrofluoric acid), 41. 
phosphide (phosphuretted hydro- 
gen), 43, 195. 
sulphide ( sulphuretted hydrogen), 
35- 
Hydrocarbons, 134. 
Hydrogen, 3, 5, 15. 

a metal, 162. 
generator, 186. 
preparation of, 15. 

I. 

Ignition, point of, 97. 
Illumination, 145. 
India-rubber, 130. 
Ink, 61, 127. 

indelible, 69. 
Iodine, 12, 40. 
Iridium, 89. 
Iron, 51. 

manufacture, 5*. 

pyrites, 34, 61. 

salts, 61. 



I Isomerism, 167. 
Isomorphioin, 166. 



Kaolin, 80, 82. 
Kelp, 76. 
Kuplernickel, 73. 



K. 



L. 



Laughing gas, 25. 
Lead, 56. 

black, 28. 

red, 62. 

salts 62. 

sugar of, 62 

white, 62. 
Leaven, 158. 
Lime, 84. 

chloride of, %j. 

l.ght, 16. 
Limestone, 84, 98. 
Litharge, 62. 
Lixiviat on, 78. 
Lunar caustic, 69. 
Lungs, described, 104. 

M. 

Magnesia, -]2, 79. 
Magnesium, 71. 

bums in air, 97. 
salts, 79. 
Maizena, 121. 
Malachite, 58. 
Manganese, 88. 

black oxide of, it, 89. 
Manures, use of, 112, 113. 
Marble, 84, 85, 98. 
Marsh-gas, 136. 
Mercury, 64. 

salts, 69. 
trough, 193. 
Metallic veins or lodes, 50. 
Metals, 49. 

fusible, 73, 89. 

noble, 64. 

melting-points of, 49. 

most useful, 51. 

ores of, 50. 

specific gravitv of, 49. 
Mica, 80. 

Milk, composition of, 103. 
Mirrors, silvering of, 65. 
Molasses, 122. 
Molecules, 9, 164. 
Monad-, dyads, triads, eta, 161. 
Mordants, '64. 
Morphine, 131. 
Mortar, 84. 
Mosaic gold, 64. 
Muriatic acid, 3, 9, 38, 77. 



N. 



Naphthaline, 139. 
Nascent state, 23. 



20S 



INDEX. 



Neutrals, 14. 
N ckel, 73. 

salts, 82. 
Nicotine, 131. 
Nipper-tap, the, 186, 
Nitnc acid, 24. 

chloride, 28. 

iod de, 28. 

oxide, 22, 33. 
Nitro-benzole, 139, 166. 
N tro-cellulose, 125. 
Nitrogen, 6, 21. 

group, 44, 73. 
properties of, 22, 27. 
Nitro-glycerine, 166. 
Nitrous oxide, 25. 



Oils, 128. 
Opium, 131. 
Organic structure, no. 
Osmose, 104. 
Oxides, acid, 13. 
basic, 14. 
names of, 13. 
neutral, 14. 
Oxyacids, 39. 
Oxygen, 5, 10. 

and carbon, 146. 

daily consumption of, 107. 

group, 35. 

making of. 191 . 

nascent state of, 37. 

partially active state of, 100. 

properties of, n. 

sulphur burned in, 191. 
Ozone- 12, 100 

way of making, 188. 

P. 

ParafEne, 135. 
Parchment, vegetable, 126. 
Parhelia, 21. 
Pearlash, 84. 
Petroleum, 140. 
Pewter, 60. 
Phosphorus, n, 25, 42, 91. 

caution in using, 192. 
burned in chlorine, 195. 
properties of, 42. 
Photography, 70, 175. 
Plants and animals, 1 19. 

earthy portion of, 112. 

food of, 1 1 1. 

growth of, 108, 116, 152. 

organic portion of, 114. 

prepare food for animals, 118. 

purify the air for animals, 117. 

structure of, 109. 
Platinum, 68. 

salts, 70. 
Plumbago, 28. 
Plumbic salts, 62. 
Pneumatic trough, the, 185. 
Polymorphism, 168. 



Porcela : n, 80. 

Pot^h, can -tic, 84. 

PotasMC carbonate, 84. 

chlorate, 84, 106. 
cyanide, 2 y 
nitrate, 84. 

Potassium, 83, 93. 

Problems, i&i. 

Prussian blue, 27. 

Putrefaction, 101. 



Q, 



Quanti valence, 161. 
Quinine, 131. 



R. 

Radicals, 27, 163. 
Reaction, n. 
Rectifying of spirits, 155. 
Resins, 130. 
Respiration, 103. 
Rochelle salts, 127. 
Rusting of metals. 102. 



s. 

Sago, i2i. 
Sal-ammoniac, 26. 
Salt, 74. 

rock, 75. 
springs, 75. 
Saltpetre, 84. 

soda, 78. 
Salts, 14, 164 
Scheele's green, 03. 
Silica, 44. 
Silicon, 44. 
Silver, 66. 

salts, 69. 
Soap, 129. 
Soda, bicarbonate oi, 78. 

caustic, 74. 
Soda-ash, 76. 
Sodic berate, 79. 

carbonate, 76. 

chloride, 74. 

hyposulphite, 79. 

nitrate, 78. 

silicate, 79. 

sulphate, 78. 

tungstate, 89. 
Sodium, 5, 71. 

salts, 74. 
Spectra, kinds 01, ]6g. 
Spectroscope, the, 168. 
Speiss, 73. 
Spirits, distillation and rectification 

155- . 
Stalactites, 85. 
Stalagmites, 86. 
Stannic salts, 64. 
Starch, 103, 120. 

converted into sugar, 124. 

kinds of, 121 
Steel, 55 



INDEX. 



209 



Strontium, 86. 

salts, 86. 
Strychnine, 131. 
Substitution, 165. 
Sugar, composition of, 105. 
fermentation of, 152. 
kinds of, 122. 

rapid combustion of, 106, 195 
Sulphides, 30. 
Sulphur, 11, 18, 30, 35. 

in eggs, etc., 67. 
properties, 31. 
supports combustion, 98. 
Sulphuretted hydrogen, 35. 
Sulphuric acid, 33. 
Sulphurous acid, 32. 
Sunlight, an agent in growth of plants, 

116. 
Symbols of compounds, 9. 
elements, 7. 



Tannin, 127. 
Tapioca, 121. 
Tartar-emetic, 82, 127. 
Tartaric acid, 126, 168. 
Tea, alkaloid in, 131. 

tannin in, 128. 
Theine, 13:. 
Tin, 59. 

alloys of, 60. 

salts, 64. 

water-pipes, 59. 
Tobacco, T31. 
Toluole, 139. 
Tungsten, 89. 
Type-metal, 73. 
Types, chemical, 164. 
condensed, 164. 



u. 



Uranium, 90. 



Veidigris, 63. 
Vermilion, 69. 
Vinegar, 156. 

wood, 134. 
Vitriol, blue, 63. 

green, 33, 35. 65. 

oil of, 33. 

white, 15, 64. 

w. 

Water, 5, 9, 17. 

as food of plants, 115. 

kinds of, 18. 

in plants and animals, 19. 

lead pipes for, 56. 

of crystallization, 18. 

tin pipes for, 59. 

uses of, 20. 
Wax, 129. 
Weights, atomic, 10. 

,, table of, 162. 
Welding, 52. 
Wolfranium, 89. 
Wood, composition of, 100, 116. 

distillation of, 134. 

naphtha, 135. 

tar, 135. 

vinegar, 134, 157. 
Woody fibre, 114, 125. 

converted into sugar, 124. 



Yeast, 152, 154, 158. 
Yellow metal, 58. 



Zaffre, Si 
Zinc, 60. 



64. 













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